76. Minimum Window Substring

public String minWindow(String s, String t) {
    
        int len1 = s.length();
        int len2 = t.length();
        
        if(len1 == 0 || len2 == 0 || len1  len2)
            return "";
        
        Map map = new HashMap();
        for(char c: t.toCharArray())
            if(map.containsKey(c))
                map.put(c, map.get(c) + 1);
            else
                map.put(c, 1);
        
        
        int left = 0;    // 当前查找的子串的开始
        int minLeft = 0;    // 总的最小子串的开始
        int minLen = len1 + 1;    // 记录最小子串的长度
        int count = 0;    // t 中匹配的字符的个数
        for(int right = 0; right ) {
            char c = s.charAt(right);
            Integer value = map.get(c);
            if(map.containsKey(c)) {
                map.put(c, --value);
                if(value >= 0) 
                    count++;
            }
            
            // 还原 Map 值
            while(count == len2) {

                if(right - left + 1 // 这个串更小
                    minLeft = left;
                    minLen = right - left + 1;
                }
                c = s.charAt(left);
                if(map.containsKey(c)) {
                    value = map.get(c);
                    map.put(c, ++value);
                    if(value > 0)
                        count--;
                }
                left++;    // 
            }
        }
        
        if(minLen > len1)
            return "";
        
        return s.substring(minLeft, minLeft + minLen);
    }