word matching from a subsequence code example

Example: word matching from a subsequence

#include <bits/stdc++.h>
using namespace std;
class Solution {
   public:
   int numMatchingSubseq(string S, vector<string>& words) {
      int n = words.size();
      map <char, vector <string> > m;
      for(int i = 0; i < words.size(); i++){
         m[words[i][0]].push_back(words[i]);
      }
      int ans = 0;
      for(int i = 0; i < S.size(); i++){
         char x = S[i];
         if(m.find(x) != m.end()){
            vector <string> temp = m[x];
            m.erase(x);
            for(int j = 0; j < temp.size(); j++){
               if(temp[j].size() == 1){
                  ans++;
               } else {
                  m[temp[j][1]].push_back(temp[j].substr(1));
               }
            }
         }
      }
      return ans;
   }
};
int main() {
   Solution ob1;
   string s = "abcde";
   vector<string> v{"a","bb","acd","ace"};
   cout << ob1.numMatchingSubseq(s, v) << endl;
   return 0;
}