KMP模板

KMP模板

struct Kmp {
    vector<int> next;

    void getNext(string p) {
        int j = 0, k = -1, n = p.size();
        next.resize(n + 1);
        next[0] = -1;
        while (j < n) {
            if (k == -1 || p[j] == p[k]) {
                next[++j] = ++k;
            } else
                k = next[k];
        }
    }

    int kmp(string s, string p) {
        int n = s.size(), m = p.size();
        int i = 0, j = 0;

        while (i < n && j < m) {
            if (j == -1 || s[i] == p[j]) {
                i ++, j ++;
            } else {
                j = next[j];
            }
        }
        if (j == m) return i;
        else return -1;
    }
};