Number of matching Subsequences leetcode

class Solution {
public:
    int numMatchingSubseq(string s, vector<string>& words) {
        // store indices of distinct characters seperately
        vector<int> char_index[26];
        for(int i=0;i<s.length();i++)
            char_index[s[i]-'a'].push_back(i);
        int ans = 0;
        for(auto str:words){
            // check str is the subsequence of s?
            int prev_char_index = -1;
            for(int i=0;i<str.length();i++){
                // finding current character position such that it is strictly greater than previous character position
                auto itr = upper_bound(char_index[str[i]-'a'].begin(),char_index[str[i]-'a'].end(),prev_char_index);
                // if position not found, don't increment answer
                if(itr==char_index[str[i]-'a'].end())
                    goto h;
                // change prev_char_index variable and assign it to the value = current position value
                prev_char_index = *itr;
            }
            // if everything smoothly happens without the encounter of goto h statement, means subsequence found
            ans++;
            h:;
        }
        return ans;
    }
};