Minimum Window Substring.java

import java.util.HashMap;

class Solution {
  public String minWindow(String s, String t) {
    if (s == null || s.length() < t.length() || s.length() == 0)
      return "";
    HashMap<Character, Integer> map = new HashMap<>();
    for (char c : t.toCharArray()) {
      map.put(c, map.getOrDefault(c, 0) + 1);
    }
    int left = 0;
    int minLen = s.length()+1;
    int minLeft = 0;
    int count = map.size();
    for (int right = 0; right < s.length(); right++) {
      if (map.containsKey(s.charAt(right))) {
        map.put(s.charAt(right), map.get(s.charAt(right)) - 1);
        if (map.get(s.charAt(right)) == 0)
          count--;
      }
      System.out.println(count);
      while (count == 0) {
        if (right - left + 1 < minLen) {
          minLeft = left;
          minLen = right - left + 1;
        }
        if (map.containsKey(s.charAt(left))) {
          map.put(s.charAt(left), map.get(s.charAt(left)) + 1);
          if (map.get(s.charAt(left)) > 0) {
            count++;
          }
        }
        left++;
      }
    }
    if (minLen > s.length()) {
      return "";
    }
    return s.substring(minLeft, minLeft + minLen);
  }
}