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].

　　

class Solution {

public:

    vector<int> findSubstring(string S, vector<string> &L) {

        // Start typing your C/C++ solution below

        // DO NOT write int main() function

        map<string, int> words;

        map<string, int> count;

        vector<int> res;

        if(L.size() == 0 || S.length() < L[0].size()*L.size() ) return res;

        for(int i = 0; i< L.size(); ++i){

            ++words[L[i]];

        }

        

        for(int i= 0; i <= S.length()- L[0].size()*L.size(); ++i)

        {

            count.clear();

            int j;

            for(j = 0; j <L.size();++j){

                string str = S.substr(i+j*L[0].size(), L[0].size());

                if(words.find(str) == words.end()) break;

                count[str]++;

                if(count[str] > words[str]) break;

            }

            if(j == L.size())

              res.push_back(i);

        }

        return res;

    }

};