class Solution {
public:
    int numMatchingSubseq(string s, vector<string>& words) {
        vector<vector<int>> pos(26);
        for (int i = 0; i < s.size(); ++i) {
            pos[s[i] - 'a'].push_back(i);
        }
        int res = words.size();
        for (auto &w : words) {
            if (w.size() > s.size()) {
                --res;
                continue;
            }
            int p = -1;
            for (char c : w) {
                auto &ps = pos[c - 'a'];
                auto it = upper_bound(ps.begin(), ps.end(), p);
                if (it == ps.end()) {
                    --res;
                    break;
                }
                p = *it;
            }
        }
        return res;
    }
};