interview.cs

//solution2("...xxx..x....xxx.", 7);
//solution("aaAbcCABBc");

static int solution2(string S, int B)
{
    if (B < 2 || S.Length == 0)
        return 0;
    var potholes = new List<int>();

    var count = 1;
    for (int i = 0; i < S.Length - 1; i++)
    {
        if (S[i] == 'x' && S[i + 1] == 'x')
            count++;
        else if (S[i] == 'x')
        {
            potholes.Add(count);
            count = 1;
        }
    }

    if (S[S.Length - 1] == 'x')
    {
        potholes.Add(count);
    }

    potholes.Sort();

    var fixedCount = 0;

    for (var i = potholes.Count - 1; i >= 0; i--)
    {
        if (potholes[i] < B)
        {
            fixedCount += potholes[i];
            B -= potholes[i] + 1;
        }
        else if (B > 1)
        {
            fixedCount += B - 1;
            break;
        }
        else if (B <= 1)
            break;
    }

    return fixedCount;
}


static int solution(string letters)
{
    if (letters.Length == 0)
        return 0;
    var lower = new Dictionary<char, int>();
    var upper = new Dictionary<char, int>();

    for (int i = 0; i < letters.Length; i++)
    {
        if (char.IsLower(letters[i]))
            lower[letters[i]] = i;
    }

    for (var i = letters.Length - 1; i >= 0; i--)
    {
        if (char.IsUpper(letters[i]))
            upper[letters[i]] = i;
    }
    var count = 0;
    foreach (var lowerItem in lower)
    {
        if (upper.TryGetValue(char.ToUpper(lowerItem.Key), out var upperIndex))
            if (upperIndex > lowerItem.Value)
                count++;
    }


    return count;

}