## Tag Archives: leetcode

## C# || How To Design Graph With Shortest Path Calculator Using C#

The following is a module with functions which demonstrates how to design graph with shortest path calculator using C#.

1. Graph – Problem Statement

There is a **directed weighted** graph that consists of **n** nodes numbered from **0** to **n – 1**. The edges of the graph are initially represented by the given array **edges** where **edges[i] = [from _{i}, to_{i}, edgeCost_{i}]** meaning that there is an edge from

**from**to

_{i}**to**with the cost

_{i}**edgeCost**.

_{i}Implement the **Graph** class:

**Graph(int n, int[][] edges)**initializes the object with**n**nodes and the given edges.**addEdge(int[] edge)**adds an edge to the list of edges where**edge = [from, to, edgeCost]**. It is guaranteed that there is no edge between the two nodes before adding this one.**int shortestPath(int node1, int node2)**returns the**minimum**cost of a path from**node1**to**node2**. If no path exists, return**-1**. The cost of a path is the sum of the costs of the edges in the path.

**Example 1:**

Input

["Graph", "shortestPath", "shortestPath", "addEdge", "shortestPath"]

[[4, [[0, 2, 5], [0, 1, 2], [1, 2, 1], [3, 0, 3]]], [3, 2], [0, 3], [[1, 3, 4]], [0, 3]]

Output

[null, 6, -1, null, 6]

Explanation

Graph g = new Graph(4, [[0, 2, 5], [0, 1, 2], [1, 2, 1], [3, 0, 3]]);

g.shortestPath(3, 2); // return 6. The shortest path from 3 to 2 in the first diagram above is 3 -> 0 -> 1 -> 2 with a total cost of 3 + 2 + 1 = 6.

g.shortestPath(0, 3); // return -1. There is no path from 0 to 3.

g.addEdge([1, 3, 4]); // We add an edge from node 1 to node 3, and we get the second diagram above.

g.shortestPath(0, 3); // return 6. The shortest path from 0 to 3 now is 0 -> 1 -> 3 with a total cost of 2 + 4 = 6.

2. Graph – Solution

The following is a solution which demonstrates how to design graph with shortest path calculator.

```
```
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// ============================================================================// Author: Kenneth Perkins// Date: Jun 1, 2024// Taken From: http://programmingnotes.org/// File: Solution.cs// Description: Demonstrates how to design graph shortest path calculator// ============================================================================/** * Your Graph object will be instantiated and called as such: * Graph obj = new Graph(n, edges); * obj.AddEdge(edge); * int param_2 = obj.ShortestPath(node1,node2); */public class Graph { List<List<KeyValuePair<int, int>>> adjList; public Graph(int n, int[][] edges) { adjList = new List<List<KeyValuePair<int, int>>>(); for (int i = 0; i < n; i++) { adjList.Add(new List<KeyValuePair<int, int>>()); } foreach (int[] e in edges) { AddEdge(e); } } public void AddEdge(int[] edge) { adjList[edge[0]].Add(new KeyValuePair<int, int>(edge[1], edge[2])); } public int ShortestPath(int node1, int node2) { int n = adjList.Count; var pq = new PriorityQueue<List<int>, List<int>>( Comparer<List<int>>.Create((a, b) => a[0].CompareTo(b[0])) ); int[] costForNode = new int[n]; Array.Fill(costForNode, int.MaxValue); costForNode[node1] = 0; var root = new List<int>() { 0, node1 }; pq.Enqueue(root, root); while (pq.Count > 0) { var curr = pq.Dequeue(); int currCost = curr[0]; int currNode = curr[1]; if (currCost > costForNode[currNode]) { continue; } if (currNode == node2) { return currCost; } foreach (var neighbor in adjList[currNode]) { int neighborNode = neighbor.Key; int cost = neighbor.Value; int newCost = currCost + cost; if (newCost < costForNode[neighborNode]) { costForNode[neighborNode] = newCost; var newPath = new List<int>() { newCost, neighborNode }; pq.Enqueue(newPath, newPath); } } } return -1; }}// http://programmingnotes.org/

**QUICK NOTES**:

The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output for the example cases:

[null,6,-1,null,6]

## C# || How To Find Largest 3 Same Digit Number In String Using C#

The following is a module with functions which demonstrates how to find the largest 3 same digit number in a string using C#.

1. Largest Good Integer – Problem Statement

You are given a string **num** representing a large integer. An integer is **good** if it meets the following conditions:

- It is a
**substring**of**num**with length**3**. - It consists of only one unique digit.

Return *the maximum good integer as a string or an empty string *

**“”**

*if no such integer exists*.

Note:

- A
**substring**is a contiguous sequence of characters within a string. - There may be
**leading zeroes**in**num**or a good integer.

**Example 1:**

Input:num = "6133339"777

Output:"777"

Explanation:There are two distinct good integers: "777" and "333".

"777" is the largest, so we return "777".

**Example 2:**

Input:num = "2319"000

Output:"000"

Explanation:"000" is the only good integer.

**Example 3:**

Input:num = "42352338"

Output:""

Explanation:No substring of length 3 consists of only one unique digit. Therefore, there are no good integers.

2. Largest Good Integer – Solution

The following is a solution which demonstrates how to find the largest 3 same digit number in a string.

```
```
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// ============================================================================// Author: Kenneth Perkins// Date: May 23, 2024// Taken From: http://programmingnotes.org/// File: Solution.cs// Description: Demonstrates how to find largest odd number in a string// ============================================================================public class Solution { public string LargestGoodInteger(string num) { // Assign 'maxDigit' to the NUL character (smallest ASCII value character) char maxDigit = '\0'; // Iterate on characters of the num string. for (int index = 0; index <= num.Length - 3; ++index) { // If 3 consecutive characters are the same, // store the character in 'maxDigit' if it's bigger than what it already stores. if (num[index] == num[index + 1] && num[index] == num[index + 2]) { maxDigit = (char) Math.Max(maxDigit, num[index]); } } // If 'maxDigit' is NUL, return an empty string; otherwise, return a string of size 3 with 'maxDigit' characters. return maxDigit == '\0' ? "" : new string(new char[]{maxDigit, maxDigit, maxDigit}); }}// http://programmingnotes.org/

**QUICK NOTES**:

The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output for the example cases:

"777"

"000"

""

## C# || How To Find Largest Odd Number In String Using C#

The following is a module with functions which demonstrates how to find the largest odd number in a string using C#.

1. Largest Odd Number – Problem Statement

You are given a string **num**, representing a large integer. Return *the largest-valued odd integer (as a string) that is a non-empty substring of *

**num**

*, or an empty string*

**“”**

*if no odd integer exists*.

A **substring** is a contiguous sequence of characters within a string.

**Example 1:**

Input:num = "52"

Output:"5"

Explanation:The only non-empty substrings are "5", "2", and "52". "5" is the only odd number.

**Example 2:**

Input:num = "4206"

Output:""

Explanation:There are no odd numbers in "4206".

**Example 3:**

Input:num = "35427"

Output:"35427"

Explanation:"35427" is already an odd number.

2. Largest Odd Number – Solution

The following is a solution which demonstrates how to find the largest odd number in a string.

```
```
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// ============================================================================// Author: Kenneth Perkins// Date: Apr 13, 2024// Taken From: http://programmingnotes.org/// File: Solution.cs// Description: Demonstrates how to find largest odd number in a string// ============================================================================public class Solution { public string LargestOddNumber(string num) { for (int index = num.Length - 1; index >= 0; --index) { if (Convert.ToInt32(num[index]) % 2 != 0) { return num.Substring(0, index + 1); } } return ""; }}// http://programmingnotes.org/

**QUICK NOTES**:

The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output for the example cases:

"5"

""

"35427"

## C# || How To Determine If A Binary Tree Is Even Odd Tree Using C#

The following is a module with functions which demonstrates how to determine if a binary tree is an even odd tree using C#.

1. Is Even Odd Tree – Problem Statement

A binary tree is named **Even-Odd** if it meets the following conditions:

- The root of the binary tree is at level index
**0**, its children are at level index**1**, their children are at level index**2**, etc. - For every
**even-indexed**level, all nodes at the level have**odd**integer values in**strictly increasing**order (from left to right). - For every
**odd-indexed**level, all nodes at the level have**even**integer values in**strictly decreasing**order (from left to right).

Given the **root** of a binary tree, *return ***true*** if the binary tree is Even-Odd, otherwise return *

**false**

*.*

**Example 1:**

Input:root = [1,10,4,3,null,7,9,12,8,6,null,null,2]

Output:true

Explanation:The node values on each level are:

Level 0: [1]

Level 1: [10,4]

Level 2: [3,7,9]

Level 3: [12,8,6,2]

Since levels 0 and 2 are all odd and increasing and levels 1 and 3 are all even and decreasing, the tree is Even-Odd.

**Example 2:**

Input:root = [5,4,2,3,3,7]

Output:false

Explanation:The node values on each level are:

Level 0: [5]

Level 1: [4,2]

Level 2: [3,3,7]

Node values in level 2 must be in strictly increasing order, so the tree is not Even-Odd.

**Example 3:**

Input:root = [5,9,1,3,5,7]

Output:false

Explanation:Node values in the level 1 should be even integers.

2. Is Even Odd Tree – Solution

The following is a solution which demonstrates how to determine if a binary tree is an even odd tree.

This solution uses breadth-first search.

```
```
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// ============================================================================// Author: Kenneth Perkins// Date: Mar 1, 2024// Taken From: http://programmingnotes.org/// File: Solution.cs// Description: Demonstrates how to determine an even odd tree// ============================================================================/** * Definition for a binary tree node. * public class TreeNode { * public int val; * public TreeNode left; * public TreeNode right; * public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) { * this.val = val; * this.left = left; * this.right = right; * } * } */public class Solution { public bool IsEvenOddTree(TreeNode root) { var queue = new Queue<TreeNode>(); queue.Enqueue(root); var isEvenLevel = true; while (queue.Count > 0) { int previousValue = isEvenLevel ? int.MinValue : int.MaxValue; for (var size = queue.Count - 1; size >= 0; --size) { var currentNode = queue.Dequeue(); if (isEvenLevel) { if (IsEven(currentNode.val) || previousValue >= currentNode.val) { return false; } } else { if (!IsEven(currentNode.val) || previousValue <= currentNode.val) { return false; } } if (currentNode.left != null) { queue.Enqueue(currentNode.left); } if (currentNode.right != null) { queue.Enqueue(currentNode.right); } previousValue = currentNode.val; } isEvenLevel = !isEvenLevel; } return true; } private bool IsEven(int value) { return value % 2 == 0; }}// http://programmingnotes.org/

**QUICK NOTES**:

The highlighted lines are sections of interest to look out for.

Once compiled, you should get this as your output for the example cases:

true

false

false

## C# || How To Group People Given The Group Size They Belong To Using C#

The following is a module with functions which demonstrates how to group people given the group size they belong to using C#.

1. Group The People – Problem Statement

There are **n** people that are split into some unknown number of groups. Each person is labeled with a **unique ID** from **0** to **n – 1**.

You are given an integer array **groupSizes**, where **groupSizes[i]** is the size of the group that person **i** is in. For example, if **groupSizes[1] = 3**, then person **1** must be in a group of size **3**.

Return *a list of groups such that each person i is in a group of size groupSizes[i]*.

Each person should appear in **exactly one group**, and every person must be in a group. If there are multiple answers, **return any of them**. It is **guaranteed** that there will be **at least one** valid solution for the given input.

**Example 1:**

Input:groupSizes = [3,3,3,3,3,1,3]

Output:[[5],[0,1,2],[3,4,6]]

Explanation:

The first group is [5]. The size is 1, and groupSizes[5] = 1.

The second group is [0,1,2]. The size is 3, and groupSizes[0] = groupSizes[1] = groupSizes[2] = 3.

The third group is [3,4,6]. The size is 3, and groupSizes[3] = groupSizes[4] = groupSizes[6] = 3.

Other possible solutions are [[2,1,6],[5],[0,4,3]] and [[5],[0,6,2],[4,3,1]].

**Example 2:**

Input:groupSizes = [2,1,3,3,3,2]

Output:[[1],[0,5],[2,3,4]]

2. Group The People – Solution

The following is a solution which demonstrates how to group people given the group size they belong to.

```
```
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// ============================================================================// Author: Kenneth Perkins// Date: Feb 14, 2024// Taken From: http://programmingnotes.org/// File: Solution.cs// Description: Demonstrates how to group people given group they belong to// ============================================================================public class Solution { public IList<IList<int>> GroupThePeople(int[] groupSizes) { var ans = new List<IList<int>>(); // A map from group size to the list of indices that are there in the group. var szToGroup = new Dictionary<int, List<int>>(); for (int i = 0; i < groupSizes.Length; i++) { if (!szToGroup.ContainsKey(groupSizes[i])) { szToGroup.Add(groupSizes[i], new List<int>()); } var group = szToGroup[groupSizes[i]]; group.Add(i); // When the list size equals the group size, empty it and store it in the answer. if (group.Count == groupSizes[i]) { ans.Add(group); szToGroup.Remove(groupSizes[i]); } } return ans; }}// http://programmingnotes.org/

**QUICK NOTES**:

The highlighted lines are sections of interest to look out for.

Once compiled, you should get this as your output for the example cases:

[[0,1,2],[5],[3,4,6]]

[[1],[2,3,4],[0,5]]

## C# || How To Find Minimum Deletions To Make Character Frequencies Unique Using C#

The following is a module with functions which demonstrates how to find the minimum deletions to make character frequencies unique using C#.

1. Min Deletions – Problem Statement

A string **s** is called **good** if there are no two different characters in **s** that have the same **frequency**.

Given a string **s**, return* the minimum number of characters you need to delete to make *

**s**

**good**.The **frequency** of a character in a string is the number of times it appears in the string. For example, in the string **“aab”**, the **frequency** of **‘a’** is **2**, while the **frequency** of **‘b’** is **1**.

**Example 1:**

Input:s = "aab"

Output:0

Explanation:`s`

is already good.

**Example 2:**

Input:s = "aaabbbcc"

Output:2

Explanation:You can delete two 'b's resulting in the good string "aaabcc".

Another way it to delete one 'b' and one 'c' resulting in the good string "aaabbc".

**Example 3:**

Input:s = "ceabaacb"

Output:2

Explanation:You can delete both 'c's resulting in the good string "eabaab".

Note that we only care about characters that are still in the string at the end (i.e. frequency of 0 is ignored).

2. Min Deletions – Solution

The following is a solution which demonstrates how to find the minimum deletions to make character frequencies unique.

```
```
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// ============================================================================// Author: Kenneth Perkins// Date: Feb 1, 2024// Taken From: http://programmingnotes.org/// File: Solution.cs// Description: Demonstrates how to find minimum deletions to make unique// ============================================================================public class Solution { public int MinDeletions(string s) { // Store the frequency of each character int[] frequency = new int[26]; for (int i = 0; i < s.Length; i++) { frequency[s[i] - 'a']++; } Array.Sort(frequency); int deleteCount = 0; // Maximum frequency the current character can have int maxFreqAllowed = s.Length; // Iterate over the frequencies in descending order for (int i = 25; i >= 0 && frequency[i] > 0; i--) { // Delete characters to make the frequency equal the maximum frequency allowed if (frequency[i] > maxFreqAllowed) { deleteCount += frequency[i] - maxFreqAllowed; frequency[i] = maxFreqAllowed; } // Update the maximum allowed frequency maxFreqAllowed = Math.Max(0, frequency[i] - 1); } return deleteCount; }}// http://programmingnotes.org/

**QUICK NOTES**:

The highlighted lines are sections of interest to look out for.

Once compiled, you should get this as your output for the example cases:

0

2

2

## C# || Reconstruct Itinerary – How To Reconstruct Itinerary In Order Using C#

The following is a module with functions which demonstrates how to reconstruct itinerary in order using C#.

1. Find Itinerary – Problem Statement

You are given a list of airline **tickets** where **tickets[i] = [from _{i}, to_{i}]** represent the departure and the arrival airports of one flight. Reconstruct the itinerary in order and return it.

All of the tickets belong to a man who departs from **“JFK”**, thus, the itinerary must begin with **“JFK”**. If there are multiple valid itineraries, you should return the itinerary that has the smallest lexical order when read as a single string.

- For example, the itinerary
**[“JFK”, “LGA”]**has a smaller lexical order than**[“JFK”, “LGB”]**.

You may assume all tickets form at least one valid itinerary. You must use all the tickets once and only once.

**Example 1:**

Input:tickets = [["MUC","LHR"],["JFK","MUC"],["SFO","SJC"],["LHR","SFO"]]

Output:["JFK","MUC","LHR","SFO","SJC"]

**Example 2:**

Input:tickets = [["JFK","SFO"],["JFK","ATL"],["SFO","ATL"],["ATL","JFK"],["ATL","SFO"]]

Output:["JFK","ATL","JFK","SFO","ATL","SFO"]

Explanation:Another possible reconstruction is ["JFK","SFO","ATL","JFK","ATL","SFO"] but it is larger in lexical order.

2. Find Itinerary – Solution

The following is a solution which demonstrates how to reconstruct itinerary in order.

```
```
1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162
// ============================================================================// Author: Kenneth Perkins// Date: Jan 1, 2024// Taken From: http://programmingnotes.org/// File: Solution.cs// Description: Demonstrates how to reconstruct itinerary in order// ============================================================================public class Solution { public IList<string> FindItinerary(IList<IList<string>> tickets) { var map = new Dictionary<string, List<string>>(); for (int index = 0; index < tickets.Count; ++index) { List<string> ticket = tickets[index].ToList(); string from = ticket[0]; string to = ticket[1]; if (!map.ContainsKey(from)) { map[from] = new List<string>(); } map[from].Add(to); } foreach (List<string> list in map.Values) { list.Sort(); } var result = new List<string>(); string start = "JFK"; result.Add(start); DFS(map, start, result, tickets.Count); return result; } private bool DFS(Dictionary<string, List<string>> map, string cur, List<string> result, int totalTicket) { if (result.Count == totalTicket + 1) { return true; } if (!map.ContainsKey(cur)) { return false; } List<string> nextList = map[cur]; for (int index = 0; index < nextList.Count; ++index) { string next = nextList[index]; if (next == null) { continue; } nextList[index] = null; result.Add(next); if (DFS(map, next, result, totalTicket)) { return true; } // back track result.RemoveAt(result.Count - 1); nextList[index] = next; } return false; }}// http://programmingnotes.org/

**QUICK NOTES**:

The highlighted lines are sections of interest to look out for.

Once compiled, you should get this as your output for the example cases:

["JFK","MUC","LHR","SFO","SJC"]

["JFK","ATL","JFK","SFO","ATL","SFO"]

## C# || How To Find Minimum Operations To Reduce X To Zero Using C#

The following is a module with functions which demonstrates how to find the minimum number of operations to reduce X to zero using C#.

1. Min Operations – Problem Statement

You are given an integer array **nums** and an integer **x**. In one operation, you can either remove the leftmost or the rightmost element from the array **nums** and subtract its value from **x**. Note that this **modifies** the array for future operations.

Return *the minimum number of operations to reduce *

**x**

*to*

**exactly****0**

*if it is possible*

*, otherwise, return*

**-1**.

**Example 1:**

Input:nums = [1,1,4,2,3], x = 5

Output:2

Explanation:The optimal solution is to remove the last two elements to reduce x to zero.

**Example 2:**

Input:nums = [5,6,7,8,9], x = 4

Output:-1

**Example 3:**

Input:nums = [3,2,20,1,1,3], x = 10

Output:5

Explanation:The optimal solution is to remove the last three elements and the first two elements (5 operations in total) to reduce x to zero.

2. Min Operations – Solution

The following is a solution which demonstrates how to find the minimum number of operations to reduce X to zero.

```
```
123456789101112131415161718192021222324252627282930313233343536
// ============================================================================// Author: Kenneth Perkins// Date: Dec 25, 2023// Taken From: http://programmingnotes.org/// File: Solution.cs// Description: Demonstrates how to find the minimum operations reduce X// ============================================================================public class Solution { public int MinOperations(int[] nums, int x) { var target = -x; foreach (int num in nums) { target += num; } // since all elements are positive, we have to take all of them if (target == 0) { return nums.Length; } var map = new Dictionary<int, int>(); map[0] = -1; var sum = 0; var res = int.MinValue; for (var index = 0; index < nums.Length; ++index) { sum += nums[index]; if (map.ContainsKey(sum - target)) { res = Math.Max(res, index - map[sum - target]); } // no need to check containsKey since sum is unique map[sum] = index; } return res == int.MinValue ? -1 : nums.Length - res; }}// http://programmingnotes.org/

**QUICK NOTES**:

The highlighted lines are sections of interest to look out for.

Once compiled, you should get this as your output for the example cases:

2

-1

5

## C# || How To Sort An Array By Parity Using C#

The following is a module with functions which demonstrates how to sort an array by parity using C#.

1. Sort Array By Parity – Problem Statement

Given an integer array **nums**, move all the even integers at the beginning of the array followed by all the odd integers.

Return * any array that satisfies this condition*.

**Example 1:**

Input:nums = [3,1,2,4]

Output:[2,4,3,1]

Explanation:The outputs [4,2,3,1], [2,4,1,3], and [4,2,1,3] would also be accepted.

**Example 2:**

Input:nums = [0]

Output:[0]

2. Sort Array By Parity – Solution

The following is a solution which demonstrates how to sort an array by parity.

```
```
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// ============================================================================// Author: Kenneth Perkins// Date: Dec 1, 2023// Taken From: http://programmingnotes.org/// File: Solution.cs// Description: Demonstrates how to sort an array by parity// ============================================================================public class Solution { public int[] SortArrayByParity(int[] nums) { var startIndex = 0; var endIndex = nums.Length -1; while (startIndex < endIndex) { if (IsOdd(nums[startIndex])) { var temp = nums[startIndex]; nums[startIndex] = nums[endIndex]; nums[endIndex] = temp; --endIndex; } else { ++startIndex; } } return nums; } private bool IsOdd(int num) { return num % 2 != 0; }}// http://programmingnotes.org/

**QUICK NOTES**:

The highlighted lines are sections of interest to look out for.

Once compiled, you should get this as your output for the example cases:

[4,2,1,3]

[0]

## C# || Parallel Courses III – How To Find Minimum Number Months To Complete All Courses Using C#

The following is a module with functions which demonstrates how to find the minimum number of months needed to complete all courses using C#.

1. Minimum Time – Problem Statement

You are given an integer **n**, which indicates that there are **n** courses labeled from **1** to **n**. You are also given a 2D integer array **relations** where **relations[j] = [prevCourse _{j}, nextCourse_{j}]** denotes that course

**prevCourse**has to be completed

_{j}**before**course

**nextCourse**(prerequisite relationship). Furthermore, you are given a

_{j}**0-indexed**integer array

**time**where

**time[i]**denotes how many

**months**it takes to complete the

**(i+1)**course.

^{th}You must find the **minimum** number of months needed to complete all the courses following these rules:

- You may start taking a course at
**any time**if the prerequisites are met. **Any number of courses**can be taken at the**same time**.

Return *the minimum number of months needed to complete all the courses*.

**Note:** The test cases are generated such that it is possible to complete every course (i.e., the graph is a directed acyclic graph).

**Example 1:**

Input:n = 3, relations = [[1,3],[2,3]], time = [3,2,5]

Output:8

Explanation:The figure above represents the given graph and the time required to complete each course.

We start course 1 and course 2 simultaneously at month 0.

Course 1 takes 3 months and course 2 takes 2 months to complete respectively.

Thus, the earliest time we can start course 3 is at month 3, and the total time required is 3 + 5 = 8 months.

**Example 2:**

Input:n = 5, relations = [[1,5],[2,5],[3,5],[3,4],[4,5]], time = [1,2,3,4,5]

Output:12

Explanation:The figure above represents the given graph and the time required to complete each course.

You can start courses 1, 2, and 3 at month 0.

You can complete them after 1, 2, and 3 months respectively.

Course 4 can be taken only after course 3 is completed, i.e., after 3 months. It is completed after 3 + 4 = 7 months.

Course 5 can be taken only after courses 1, 2, 3, and 4 have been completed, i.e., after max(1,2,3,7) = 7 months.

Thus, the minimum time needed to complete all the courses is 7 + 5 = 12 months.

2. Minimum Time – Solution

The following is a solution which demonstrates how to find the minimum number of months needed to complete all courses.

```
```
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// ============================================================================// Author: Kenneth Perkins// Date: Nov 1, 2023// Taken From: http://programmingnotes.org/// File: Solution.cs// Description: Demonstrates how to find the minimum months complete courses// ============================================================================public class Solution { public int MinimumTime(int n, int[][] relations, int[] time) { var graph = new Dictionary<int, List<int>>(); for (int i = 0; i < n; i++) { graph[i] = new List<int>(); } int[] indegree = new int[n]; foreach (int[] edge in relations) { int x = edge[0] - 1; int y = edge[1] - 1; graph[x].Add(y); indegree[y]++; } var queue = new Queue<int>(); int[] maxTime = new int[n]; for (int node = 0; node < n; node++) { if (indegree[node] == 0) { queue.Enqueue(node); maxTime[node] = time[node]; } } while (queue.Count > 0) { int node = queue.Dequeue(); foreach (int neighbor in graph[node]) { maxTime[neighbor] = Math.Max(maxTime[neighbor], maxTime[node] + time[neighbor]); indegree[neighbor]--; if (indegree[neighbor] == 0) { queue.Enqueue(neighbor); } } } int ans = 0; for (int node = 0; node < n; node++) { ans = Math.Max(ans, maxTime[node]); } return ans; }}// http://programmingnotes.org/

**QUICK NOTES**:

The highlighted lines are sections of interest to look out for.

Once compiled, you should get this as your output for the example cases:

8

12

## C# || How To Find Largest Value In Each Binary Tree Row Using C#

The following is a module with functions which demonstrates how to find the largest value in each binary tree row using C#.

1. Largest Values – Problem Statement

Given the **root** of a binary tree, return *an array of the largest value in each row* of the tree **(0-indexed)**.

**Example 1:**

Input:root = [1,3,2,5,3,null,9]

Output:[1,3,9]

**Example 2:**

Input:root = [1,2,3]

Output:[1,3]

2. Largest Values – Solution

The following is a solution which demonstrates how to find the largest value in each binary tree row.

```
```
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// ============================================================================// Author: Kenneth Perkins// Date: Oct 28, 2023// Taken From: http://programmingnotes.org/// File: Solution.cs// Description: Demonstrates how to find the largest value binary tree row// ============================================================================/** * Definition for a binary tree node. * public class TreeNode { * public int val; * public TreeNode left; * public TreeNode right; * public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) { * this.val = val; * this.left = left; * this.right = right; * } * } */public class Solution { public IList<int> LargestValues(TreeNode root) { if (root == null) { return new List<int>(); } var ans = new List<int>(); var queue = new Queue<TreeNode>(); queue.Enqueue(root); while (queue.Count > 0) { int currMax = int.MinValue; for (int i = queue.Count -1; i >= 0; --i) { var node = queue.Dequeue(); currMax = Math.Max(currMax, node.val); if (node.left != null) { queue.Enqueue(node.left); } if (node.right != null) { queue.Enqueue(node.right); } } ans.Add(currMax); } return ans; }}// http://programmingnotes.org/

**QUICK NOTES**:

The highlighted lines are sections of interest to look out for.

Once compiled, you should get this as your output for the example cases:

[1,3,9]

[1,3]

## C# || How To Find The Minimum Speed To Arrive On Time Using C#

The following is a module with functions which demonstrates how to find the minimum speed to arrive on time using C#.

1. Min Speed On Time – Problem Statement

You are given a floating-point number **hour**, representing the amount of time you have to reach the office. To commute to the office, you must take **n** trains in sequential order. You are also given an integer array **dist** of length **n**, where **dist[i]** describes the distance (in kilometers) of the **i ^{th}** train ride.

Each train can only depart at an integer hour, so you may need to wait in between each train ride.

- For example, if the
**1**train ride takes^{st}**1.5**hours, you must wait for an additional**0.5**hours before you can depart on the**2**train ride at the 2 hour mark.^{nd}

Return *the minimum positive integer speed (in kilometers per hour) that all the trains must travel at for you to reach the office on time, or *

**-1**

*if it is impossible to be on time*.

Tests are generated such that the answer will not exceed **10 ^{7}** and

**hour**will have

**at most two digits after the decimal point**.

**Example 1:**

Input:dist = [1,3,2], hour = 6

Output:1

Explanation:At speed 1:

- The first train ride takes 1/1 = 1 hour.

- Since we are already at an integer hour, we depart immediately at the 1 hour mark. The second train takes 3/1 = 3 hours.

- Since we are already at an integer hour, we depart immediately at the 4 hour mark. The third train takes 2/1 = 2 hours.

- You will arrive at exactly the 6 hour mark.

**Example 2:**

Input:dist = [1,3,2], hour = 2.7

Output:3

Explanation:At speed 3:

- The first train ride takes 1/3 = 0.33333 hours.

- Since we are not at an integer hour, we wait until the 1 hour mark to depart. The second train ride takes 3/3 = 1 hour.

- Since we are already at an integer hour, we depart immediately at the 2 hour mark. The third train takes 2/3 = 0.66667 hours.

- You will arrive at the 2.66667 hour mark.

**Example 3:**

Input:dist = [1,3,2], hour = 1.9

Output:-1

Explanation:It is impossible because the earliest the third train can depart is at the 2 hour mark.

2. Min Speed On Time – Solution

The following is a solution which demonstrates how to find the minimum speed to arrive on time.

```
```
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// ============================================================================// Author: Kenneth Perkins// Date: Sep 1, 2023// Taken From: http://programmingnotes.org/// File: Solution.cs// Description: Demonstrates how to find the minimum speed to arrive on time// ============================================================================public class Solution { public int MinSpeedOnTime(int[] dist, double hour) { int left = 1; int right = 10000000; int minSpeed = -1; while (left <= right) { int mid = left + (right - left) / 2; // Move to the left half. if (TimeRequired(dist, mid) <= hour) { minSpeed = mid; right = mid - 1; } else { // Move to the right half. left = mid + 1; } } return minSpeed; } double TimeRequired(int[] dist, int speed) { double time = 0.0; for (int i = 0 ; i < dist.Length; i++) { double t = (double) dist[i] / (double) speed; // Round off to the next integer, if not the last ride. time += (i == dist.Length - 1 ? t : Math.Ceiling(t)); } return time; }}// http://programmingnotes.org/

**QUICK NOTES**:

The highlighted lines are sections of interest to look out for.

Once compiled, you should get this as your output for the example cases:

1

3

-1

## C# || How To Find The Minimum ASCII Delete Sum for Two Strings Using C#

The following is a module with functions which demonstrates how to find the minimum ASCII delete sum for two strings using C#.

1. Minimum Delete Sum – Problem Statement

Given two strings **s1** and **s2**, return *the lowest ASCII sum of deleted characters to make two strings equal*.

**Example 1:**

Input:s1 = "sea", s2 = "eat"

Output:231

Explanation:Deleting "s" from "sea" adds the ASCII value of "s" (115) to the sum.

Deleting "t" from "eat" adds 116 to the sum.

At the end, both strings are equal, and 115 + 116 = 231 is the minimum sum possible to achieve this.

**Example 2:**

Input:s1 = "delete", s2 = "leet"

Output:403

Explanation:Deleting "dee" from "delete" to turn the string into "let",

adds 100[d] + 101[e] + 101[e] to the sum.

Deleting "e" from "leet" adds 101[e] to the sum.

At the end, both strings are equal to "let", and the answer is 100+101+101+101 = 403.

If instead we turned both strings into "lee" or "eet", we would get answers of 433 or 417, which are higher.

2. Minimum Delete Sum – Solution

The following is a solution which demonstrates how to find the minimum ASCII delete sum for two strings.

```
```
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// ============================================================================// Author: Kenneth Perkins// Date: Aug 28, 2023// Taken From: http://programmingnotes.org/// File: Solution.cs// Description: Demonstrates how to find minimum ASCII delete sum two string// ============================================================================public class Solution { public int MinimumDeleteSum(string s1, string s2) { // Make sure s2 is smaller string if (s1.Length < s2.Length) { return MinimumDeleteSum(s2, s1); } // Case for empty s1 int m = s1.Length, n = s2.Length; int[] currRow = new int[n + 1]; for (int j = 1; j <= n; j++) { currRow[j] = currRow[j - 1] + s2[j - 1]; } // Compute answer row-by-row for (int i = 1; i <= m; i++) { int diag = currRow[0]; currRow[0] += s1[i - 1]; for (int j = 1; j <= n; j++) { int answer; // If characters are the same, the answer is top-left-diagonal value if (s1[i - 1] == s2[j - 1]) { answer = diag; } // Otherwise, the answer is minimum of top and left values with // deleted character's ASCII value else { answer = Math.Min( s1[i - 1] + currRow[j], s2[j - 1] + currRow[j - 1] ); } // Before overwriting currRow[j] with answer, save it in diag // for the next column diag = currRow[j]; currRow[j] = answer; } } // Return the answer return currRow[n]; }}// http://programmingnotes.org/

**QUICK NOTES**:

The highlighted lines are sections of interest to look out for.

Once compiled, you should get this as your output for the example cases:

231

403

## C# || Fruit Into Baskets – How To Find The Maximum Number Of Fruits Using C#

The following is a module with functions which demonstrates how to find the maximum number of fruits using C#.

1. Total Fruit – Problem Statement

You are visiting a farm that has a single row of fruit trees arranged from left to right. The trees are represented by an integer array **fruits** where **fruits[i]** is the **type** of fruit the **i ^{th}** tree produces.

You want to collect as much fruit as possible. However, the owner has some strict rules that you must follow:

- You only have
**two**baskets, and each basket can only hold a**single type**of fruit. There is no limit on the amount of fruit each basket can hold. - Starting from any tree of your choice, you must pick
**exactly one fruit**from**every**tree (including the start tree) while moving to the right. The picked fruits must fit in one of your baskets. - Once you reach a tree with fruit that cannot fit in your baskets, you must stop.

Given the integer array **fruits**, return *the maximum number of fruits you can pick*.

**Example 1:**

Input:fruits = [1,2,1]

Output:3

Explanation:We can pick from all 3 trees.

**Example 2:**

Input:fruits = [0,1,2,2]

Output:3

Explanation:We can pick from trees [1,2,2].

If we had started at the first tree, we would only pick from trees [0,1].

**Example 3:**

Input:fruits = [1,2,3,2,2]

Output:4

Explanation:We can pick from trees [2,3,2,2].

If we had started at the first tree, we would only pick from trees [1,2].

2. Total Fruit – Solution

The following is a solution which demonstrates how to find the maximum number of fruits.

```
```
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// ============================================================================// Author: Kenneth Perkins// Date: Jul 28, 2023// Taken From: http://programmingnotes.org/// File: Solution.cs// Description: Demonstrates how to find the maximum number of fruits// ============================================================================public class Solution { public int TotalFruit(int[] fruits) { // We use a hash map 'basket' to store the number of each type of fruit. var basket = new Dictionary<int, int>(); int left = 0; int maxPicked = 0; // Add fruit from the right index (right) of the window. for (int right = 0; right < fruits.Length; ++right) { basket[fruits[right]] = basket.GetValueOrDefault(fruits[right], 0) + 1; // If the current window has more than 2 types of fruit, // we remove fruit from the left index (left) of the window, // until the window has only 2 types of fruit. while (basket.Count > 2) { basket[fruits[left]] = basket[fruits[left]] - 1; if (basket[fruits[left]] == 0) { basket.Remove(fruits[left]); } ++left; } // Update maxPicked. maxPicked = Math.Max(maxPicked, right - left + 1); } // Return maxPicked as the maximum number of fruits we can collect. return maxPicked; }}// http://programmingnotes.org/

**QUICK NOTES**:

The highlighted lines are sections of interest to look out for.

Once compiled, you should get this as your output for the example cases:

3

3

4