找出字符串中所有字母异位词

    vector<int> findAnagrams(string s, string t) {
        unordered_map<char, int> needs;
        unordered_map<char, int> window;
        for(char c : t){
            ++needs[c];
        }
        int match = 0, start = 0, left = 0, right = 0, len = s.length(), minLen = INT_MAX;
        vector<int> res;
        while(right < len){
            char c1 = s[right];
            if(needs.count(c1)){
                ++window[c1];
                if(window[c1] == needs[c1]){
                    ++match;
                }
            }
            ++right;
            while(match == needs.size()){
                if(right - left == t.size()){
                    res.push_back(left);
                }
                char c2 = s[left];
                if(needs.count(c2)){
                    --window[c2];
                    if(window[c2] < needs[c2]){
                        --match;
                    }
                }
                ++left;
            }
        }
        return res;
    }