First non-repeating character — C# Programming

Problem

Find first non-repeating char in "swiss" (answer: w).

Hints

Use Dictionary or LINQ GroupBy for frequencies.

Your practice code

Ready — edit the code above and click Run.

Solution

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main()
    {
        string s = "swiss";
        var freq = s.GroupBy(c => c).ToDictionary(g => g.Key, g => g.Count());
        char result = s.First(c => freq[c] == 1);
        Console.WriteLine(result);
    }
}

Try solving on your own first, then reveal the official answer.

Explanation

Frequency map then scan original string for count==1—common Amazon/Google style question.