30. 串联所有单词的子串(LeetCode困难)(哈希滑动窗口)

30. 串联所有单词的子串

class Solution {
public:
    vector<int> findSubstring(string s, vector<string>& words) {
        vector<int> res;
        int n = s.size(), m = words.size(), w = words[0].size();
        unordered_map<string, int> mp;
        for(auto &x : words) mp[x]++;

        for(int i = 0; i < w; ++i){
            unordered_map<string, int> tmp;
            int cnt = 0;
            for(int j = i; j + w <= n; j += w){
                if(j >= i + m * w){
                    auto word = s.substr(j - m * w, w);
                    tmp[word]--;
                    if(tmp[word] < mp[word]) --cnt;
                }
                auto word = s.substr(j, w);
                tmp[word]++;
                if(tmp[word] <= mp[word]) ++cnt;
                if(cnt == m) res.push_back(j - (m - 1) * w);    
            }
        }
        return res;
    }
};