## 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.

``` 2. Min Operations - Solution C# // ============================================================================ // 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/ 1234567891011121314151617181920212223242526272829303132333435 // ============================================================================//    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.

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:

``` 0 2 2 ```