[LeetCode] Substring with Concatenation of All Words

You are given a string, S, and a list of words, L, that are all of the same length. Find all starting indices of substring(s) in S that is a concatenation of each word in L exactly once and without any intervening characters. For example, given:
S: "barfoothefoobarman"
L: ["foo", "bar"]

You should return the indices: [0,9]. (order does not matter).

思路：利用hash map。

代码：

class Solution {
public:
    vector<int> findSubstring(string S, vector<string> &L) {
        vector<int> res;
        int num = L.size();
        int len = L[0].size();
        if (num==0){return res;}
        map<string,int> mp;  
        for (int i=0;i<num;i++){mp[L[i]]++;}      
          
        int i=0;
        while ((i+num*len-1)<S.size()){
            map<string,int> mp2;
            int j=0;
            while (j<num){
                string subs = S.substr(i+j*len,len);
                if (mp.find(subs)==mp.end()){
                        break;
                }else{
                    mp2[subs]++;
                    if (mp2[subs]>mp[subs]){
                        break;
                    }
                    j++;  
                }
            }
            if (j==num){res.push_back(i);}
            i++;
        }
      
        return res;
    }
};