LC332T4

class Solution {
public:
    int minimumScore(string s, string t) {
        int sn = s.size(), tn = t.size();
        vector<int> pref(sn), post(sn);

        pref[0] = s[0] == t[0] ? 1 : 0;
        for (int i = 1; i < sn; ++i) {
            if (pref[i-1] < tn)
                pref[i] = s[i] == t[pref[i-1]] ? pref[i-1] + 1 : pref[i-1];
            else
                pref[i] = tn;
        }

        post[sn-1] = s[sn-1] == t[tn-1] ? 1 : 0;
        for (int i = sn - 2; i >= 0; --i) {
            if (post[i+1] < tn)
                post[i] = s[i] == t[tn - 1 - post[i+1]] ? post[i+1] + 1 : post[i+1];
            else
                post[i] = tn;
        }

        int ret = INT_MAX;
        for (int i = 0; i + 1 < sn; ++i) ret = min(ret, max(tn - (pref[i] + post[i + 1]), 0));
        ret = min(ret, tn - pref[sn - 1]);
        ret = min(ret, tn - post[0]);
        return ret;
    }
};