76. Minimum Window Substring

https://leetcode.com/problems/minimum-window-substring/discuss/26808/Here-is-a-10-line-template-that-can-solve-most-'substring'-problems

 

 

class Solution {
    public String minWindow(String s, String t) {
        if(s.length() == 0) return "";
        int[] map = new int[128];
        int count = 0;
        int min = Integer.MAX_VALUE;
        for(char c : t.toCharArray()){
            map[c]++;
            count++;
        }
        int begin = 0, end = 0;
        int index = 0;
        while(end < s.length()){
            if(map[s.charAt(end)]-- > 0){
                count--;
            }
            end++;
            while(count == 0){
                if(map[s.charAt(begin)]++ == 0){
                    count++;
                }
                begin++;
                if((end - begin + 1) < min){  //小于的话才更新index
                    min = end - begin + 1;
                    index = begin-1;
                }
            }
        }
        return min == Integer.MAX_VALUE? "" : s.substring(index, index + min);
        
    }
}