class Solution {
    public String minWindow(String s, String t) {
        HashMap<Character, Integer> window = new HashMap<>(), need = new HashMap<>();
        for(char c : t.toCharArray()) need.merge(c, 1, Integer::sum);
        int cnt = 0, start = 0, len = Integer.MAX_VALUE;

        for(int l = 0, r = 0; r < s.length(); r++){
            // 窗口增大的逻辑
            char c = s.charAt(r);
            if(need.containsKey(c)){
                window.merge(c, 1, Integer::sum);
                if(need.get(c).equals(window.get(c))) cnt++;
            }

            while(cnt == need.size()){  // 窗口何时缩小
                // 更新答案
                if(len > r - l + 1){
                    len = r - l + 1;
                    start = l;
                }
                // 窗口缩小的逻辑
                c = s.charAt(l++);
                if(need.containsKey(c)){
                    if(need.get(c).equals(window.get(c))) cnt--;
                    window.merge(c, -1, Integer::sum);
                }
            }
        }

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

class Solution {
    public String minWindow(String s, String t) {
        char[] chs = s.toCharArray(), cht = t.toCharArray();
        int[] hash = new int[128];
        for(char c : cht) hash[c]--;
        int cnt = 0, m = cht.length;
        String res = "";

        for(int l = 0, r = 0; r < chs.length; r++){
            hash[chs[r]]++;
            if(hash[chs[r]] <= 0) cnt++;

            while(cnt == m && hash[chs[l]] > 0) hash[chs[l++]]--;
            
            if(cnt == m){
                if(res.equals("") || res.length() > r - l + 1){
                    res = s.substring(l, r + 1);
                }
            }
        }

        return res;
    }
}

class Solution {
    public String minWindow(String s, String t) {
        int i = 0;
        HashMap<Character, Integer> mapS = new HashMap<>();
        HashMap<Character, Integer> mapT = new HashMap<>();
        for(char c : t.toCharArray()){
            //mapT.merge(c, 1, Integer::sum);
            mapT.put(c, mapT.getOrDefault(c, 0) + 1);
        }
        int cnt = 0;
        int res = Integer.MAX_VALUE, left = 0, right = 0;

        for(int j = 0; j < s.length(); j++){
            char c = s.charAt(j);
            if(mapT.containsKey(c)){
                //mapS.merge(c, 1, Integer::sum);
                mapS.put(c, mapS.getOrDefault(c, 0) + 1);
                if(mapS.get(c).equals(mapT.get(c))){  // 一个坑：Integer 相等比较应该用 equals，而不是 ==
                    cnt++;
                }
            }
            
            while(cnt == mapT.size()){
                if(res > j - i + 1){
                    left = i;
                    right = j;
                    res = j - i + 1;
                }
                c = s.charAt(i++);
                if(mapT.containsKey(c)){
                    //mapS.merge(c, -1, Integer::sum);
                    mapS.put(c, mapS.getOrDefault(c, 0) - 1);
                    if(mapS.get(c).compareTo(mapT.get(c)) < 0){
                        cnt--;
                    }
                }
            }

        }

        return res == Integer.MAX_VALUE ? "" : s.substring(left, right + 1);
    }
}