74th LeetCode Weekly Contest Valid Number of Matching Subsequences

Given string S and a dictionary of words words, find the number of words[i] that is a subsequence of S.

Example :
Input:
S = "abcde"
words = ["a", "bb", "acd", "ace"]
Output: 3
Explanation: There are three words in words that are a subsequence of S: "a", "acd", "ace".

Note:

• All words in words and S will only consists of lowercase letters.
• The length of S will be in the range of [1, 50000].
• The length of words will be in the range of [1, 5000].
• The length of words[i] will be in the range of [1, 50].

问S中有多少符合words里面的单词（可以不连续哦）

当然是二分啊，我们保存S中字母的位置，对于每个words我们都查找字母的位置，然后+1一位继续找

 class Solution {
 public:
     int numMatchingSubseq(string S, vector<string>& words) {
         int num=;
         vector<int>vec[];
         int len=S.size();
         for(int i=;i<len;i++){
             vec[S[i]-'a'].push_back(i);
         }
         for(auto word:words){
             int add=;
             int wordLen=word.size();
             int flag=;
            // cout<<word<<endl;
             for(int i=;i<wordLen;i++){
                 if(vec[word[i]-'a'].size()==){
                     flag=;
                     break;
                 }
                 auto it=lower_bound(vec[word[i]-'a'].begin(),vec[word[i]-'a'].end(),add);
                 if(it==vec[word[i]-'a'].end()){
                     flag=;
                     break;
                 }
                 add=(*it);
                 add++;
               //  cout<<add<<endl;
             }
             if(flag){
                 num++;
             }
         }
         return num;
     }
 };