_76_minimum_window_substr.java

public class _76_minimum_window_substr {
    private Boolean isValid(int[]tFreqMap, int[]sFreqMap){
        for(int i=0 ; i<128 ; i++){
            if(sFreqMap[i]<tFreqMap[i]){
                return false;
            }
        }
        return true;
    }

    public String minWindow(String s, String t) {
        int[] tFreqMap = new int[128];
        int[] sFreqMap = new int[128];
        for(int i =0; i<t.length() ; i++){
            tFreqMap[t.charAt(i)]++;
        }
        String solution="";
        int minSolLength = Integer.MAX_VALUE;
        int left = 0;
        int right = 0;
        
        while(right<s.length()){
            sFreqMap[s.charAt(right)]++;

            while(isValid(tFreqMap, sFreqMap)){
                if(s.substring(left, right+1).length()<minSolLength){
                    solution = s.substring(left, right+1);
                    minSolLength = solution.length();
                }
                sFreqMap[s.charAt(left)]--;
                left++;
            }

            if(right<s.length()-1){
                right++;
            }else break;
        }
        return solution;
    }
}