Longest Substring Without Repeating Characters

solution.cs

public class Solution
{
    public int LengthOfLongestSubstring(string s)
    {
        var given = s.ToCharArray();

        var charsPositions = new Dictionary<char, int>();

        int startPosition = 0, maxLength = 0;

        for (var endPosition = 0;  endPosition < given.Count(); endPosition++)
        {
            var ch = given[endPosition];

            if (!charsPositions.ContainsKey(ch))
            {
                charsPositions.Add(ch, endPosition);
                maxLength = Math.Max(maxLength, charsPositions.Count);
            }
            else
            {
                var prevCharPosition = charsPositions[ch];

                foreach (var charToRemove in given[startPosition..prevCharPosition])
                {
                    charsPositions.Remove(charToRemove);
                }

                charsPositions[ch] = endPosition;

                startPosition = prevCharPosition + 1;
            }
        }

        return maxLength;
    }
}