LeetCode-Substring with Concatenation of All Words

题目:

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].

源码:

用两个map,其中一个map用来保存L中每个word出现的次数。然后遍历S字符串,通过比较word_counts中的单词出现的次数.若超过或不出现则break.

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

      int size=L.size();

      if(size<=0) return vector<int>();

      

      map<string,int> word_counts;

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

          word_counts[L[i]]++;

      }

      

      int word_size=L[0].size();

      map<string,int> counting;

      vector<int> result;

      

      for(int i=0;i<=((int)S.length()-size*word_size);i++){

            counting.clear();

            

            for(int j=0;j<size;j++){

                 string word=S.substr(i+j*word_size,word_size);

                 

                 if(word_counts.find(word)!=word_counts.end()){

                        counting[word]++;

                        

                        if(counting[word]>word_counts[word]) break;

                 }

                 

            }

            

            if(j==size) result,push_back(i);

      }

      return result;

}