C# || Accounts Merge – How To Merge A List Of Emails Using C#

November 28, 2021 admin No comments

The following is a module with functions which demonstrates how to merge a list of emails using C#.

1. Accounts Merge – Problem Statement

Given a list of accounts where each element accounts[i] is a list of strings, where the first element accounts[i][0] is a name, and the rest of the elements are emails representing emails of the account.

Now, we would like to merge these accounts. Two accounts definitely belong to the same person if there is some common email to both accounts. Note that even if two accounts have the same name, they may belong to different people as people could have the same name. A person can have any number of accounts initially, but all of their accounts definitely have the same name.

After merging the accounts, return the accounts in the following format: the first element of each account is the name, and the rest of the elements are emails in sorted order. The accounts themselves can be returned in any order.

Example 1:

Input: accounts = [["John","[email protected]","[email protected]"],["John","[email protected]","[email protected]"],["Mary","[email protected]"],["John","[email protected]"]] Output: [["John","[email protected]","[email protected]","[email protected]"],["Mary","[email protected]"],["John","[email protected]"]] Explanation: The first and second John's are the same person as they have the common email "[email protected]". The third John and Mary are different people as none of their email addresses are used by other accounts. We could return these lists in any order, for example the answer [['Mary', '[email protected]'], ['John', '[email protected]'], ['John', '[email protected]', '[email protected]', '[email protected]']] would still be accepted.

Example 2:

Input: accounts = [["Gabe","[email protected]","[email protected]","[email protected]"],["Kevin","[email protected]","[email protected]","[email protected]"],["Ethan","[email protected]","[email protected]","[email protected]"],["Hanzo","[email protected]","[email protected]","[email protected]"],["Fern","[email protected]","[email protected]","[email protected]"]] Output: [["Ethan","[email protected]","[email protected]","[email protected]"],["Gabe","[email protected]","[email protected]","[email protected]"],["Hanzo","[email protected]","[email protected]","[email protected]"],["Kevin","[email protected]","[email protected]","[email protected]"],["Fern","[email protected]","[email protected]","[email protected]"]]

2. Accounts Merge – Solution

The following is a solution which demonstrates how to merge a list of emails.

The following solution uses a union find set to group accounts with matching emails together.





		
		
			2. Accounts Merge - Solution
			
C#
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Nov 28, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to merge a list of emails
// ============================================================================
public class Solution {
    public IList<IList<string>> AccountsMerge(IList<IList<string>> accounts) {
        var set = new UnionFindSet(accounts.Count);

        // Map email to their component index
        var emailComponents = new Dictionary<string, int>();
        for (int i = 0; i < accounts.Count; ++i) {
            var account = accounts[i];

            for (int j = 1; j < account.Count; ++j) {
                var email = account[j];

                // Assign component group as the account index
                var group = i;
                if (!emailComponents.ContainsKey(email)) {
                    emailComponents[email] = group;
                } else {
                    // Union this group with the previous group of the email
                    set.Union(group, emailComponents[email]);
                }
            }
        }

        // Store emails corresponding to the components parent
        var emailGroups = new Dictionary<int, List<string>>();
        foreach (var email in emailComponents.Keys) {
            var group = emailComponents[email];
            var groupParent = set.Find(group);

            if (!emailGroups.ContainsKey(groupParent)) {
                emailGroups[groupParent] = new List<string>();
            }
            emailGroups[groupParent].Add(email);
        }

        // Sort the emails and add the account name
        var result = new List<IList<string>>();
        foreach (var group in emailGroups.Keys) {
            var emails = emailGroups[group];
            emails.Sort(StringComparer.Ordinal);
            emails.Insert(0, accounts[group][0]);
            result.Add(emails);
        }
        return result;
    }

    public class UnionFindSet {
        int[] parent;
        int[] size;

        public UnionFindSet(int count) {
            parent = new int[count];
            size = new int[count];
            for (int index = 0; index < count; ++index) {
                parent[index] = index;
                size[index] = 1;
            }
        }
        public int Find(int x) {
            if (parent[x] != x) {
                parent[x] = Find(parent[x]);
            }
            return parent[x];
        }
        public void Union(int x, int y) {
            var parentX = Find(x);
            var parentY = Find(y);
            if (parentX == parentY) {
                return;
            }
            if (size[parentX] >= size[parentY]) {
                size[parentX] += size[parentY];
                parent[parentY] = parentX;
            } else {
                size[parentY] += size[parentX];
                parent[parentX] = parentY;
            }
        }
    }
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Nov 28, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to merge a list of emails
// ============================================================================
public class Solution {
    public IList<IList<string>> AccountsMerge(IList<IList<string>> accounts) {
        var set = new UnionFindSet(accounts.Count);
 
        // Map email to their component index
        var emailComponents = new Dictionary<string, int>();
        for (int i = 0; i < accounts.Count; ++i) {
            var account = accounts[i];
 
            for (int j = 1; j < account.Count; ++j) {
                var email = account[j];
 
                // Assign component group as the account index
                var group = i;
                if (!emailComponents.ContainsKey(email)) {
                    emailComponents[email] = group;
                } else {
                    // Union this group with the previous group of the email
                    set.Union(group, emailComponents[email]);
                }
            }
        }
 
        // Store emails corresponding to the components parent
        var emailGroups = new Dictionary<int, List<string>>();
        foreach (var email in emailComponents.Keys) {
            var group = emailComponents[email];
            var groupParent = set.Find(group);
 
            if (!emailGroups.ContainsKey(groupParent)) {
                emailGroups[groupParent] = new List<string>();
            }
            emailGroups[groupParent].Add(email);
        }
 
        // Sort the emails and add the account name
        var result = new List<IList<string>>();
        foreach (var group in emailGroups.Keys) {
            var emails = emailGroups[group];
            emails.Sort(StringComparer.Ordinal);
            emails.Insert(0, accounts[group][0]);
            result.Add(emails);
        }
        return result;
    }
 
    public class UnionFindSet {
        int[] parent;
        int[] size;
 
        public UnionFindSet(int count) {
            parent = new int[count];
            size = new int[count];
            for (int index = 0; index < count; ++index) {
                parent[index] = index;
                size[index] = 1;
            }
        }
        public int Find(int x) {
            if (parent[x] != x) {
                parent[x] = Find(parent[x]);
            }
            return parent[x];
        }
        public void Union(int x, int y) {
            var parentX = Find(x);
            var parentY = Find(y);
            if (parentX == parentY) {
                return;
            }
            if (size[parentX] >= size[parentY]) {
                size[parentX] += size[parentY];
                parent[parentY] = parentX;
            } else {
                size[parentY] += size[parentX];
                parent[parentX] = parentY;
            }
        }
    }
}// 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:

[["John","[email protected]","[email protected]","[email protected]"],["Mary","[email protected]"],["John","[email protected]"]] [["Gabe","[email protected]","[email protected]","[email protected]"],["Kevin","[email protected]","[email protected]","[email protected]"],["Ethan","[email protected]","[email protected]","[email protected]"],["Hanzo","[email protected]","[email protected]","[email protected]"],["Fern","[email protected]","[email protected]","[email protected]"]]

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Posted in: C#, Console Tags: c-sharp, leetcode, Union Find

C# || Accounts Merge – How To Merge A List Of Emails Using C#

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