438. Find All Anagrams in a String

FindAnagrams.cs

public class Solution {
  public IList<int> FindAnagrams(string s, string p) {
    var pFreq = new int[26];
    var sIndex = 0;
    var ans = new List<int>();
      
    foreach(var letter in p)
      pFreq[letter - 'a']++;
    
    while(sIndex < s.Length){
      if(pFreq[s[sIndex] - 'a'] != 0){
        var j = 0;
        var wFreq = new int[26];
        var found = true;
        while(j < p.Length && j + sIndex < s.Length){
          var curKey = s[j + sIndex] - 'a';
          if(pFreq[curKey] == 0){
            found = false;
            break;
          }
          wFreq[curKey]++;
          if(wFreq[curKey] > pFreq[curKey]){
            found = false;
            break;
          }
          j++;
        }
        if(found){
          var fEq = true;
          for(var i = 0; i < 26; i++){
            if(pFreq[i] != wFreq[i]){
              fEq = false;
              break;
            }
          }
          if(fEq)
            ans.Add(sIndex);
        }
      }
      sIndex++;
    }
    return ans;
  }
}