Minimum Window Substring

LEETCODE PROBLEM SOLVING
PROBLEM->MINUMUM WINDOW SUBSTRING
import java.util.*;

class Solution {

    public String minWindow(String s, String t) {

        if (s.length() < t.length()) {
            return "";
        }


        Map<Character,Integer> need = new HashMap<>();

        for(char c : t.toCharArray()) {
            need.put(
                c,
                need.getOrDefault(c,0)+1
            );
        }


        Map<Character,Integer> window =
            new HashMap<>();


        int left = 0;
        int formed = 0;

        int required = need.size();


        int minLen = Integer.MAX_VALUE;
        int start = 0;


        for(int right = 0; right < s.length(); right++) {


            char c = s.charAt(right);

            window.put(
                c,
                window.getOrDefault(c,0)+1
            );
            if(need.containsKey(c) &&
               window.get(c).intValue()
               == need.get(c).intValue()) {

                formed++;
            }
            while(formed == required) {


                if(right-left+1 < minLen) {

                    minLen = right-left+1;
                    start = left;
                }



                char leftChar = s.charAt(left);


                window.put(
                    leftChar,
                    window.get(leftChar)-1
                );


                if(need.containsKey(leftChar) &&
                   window.get(leftChar)
                   < need.get(leftChar)) {

                    formed--;
                }


                left++;
            }
        }


        return minLen == Integer.MAX_VALUE
                ? ""
                : s.substring(start,start+minLen);
    }
}