public int strStr(String haystack, String needle) {
        char[] s = haystack.toCharArray();
        char[] t = needle.toCharArray();
        int[] next = new int[t.length];
        for (int h = 1, q = 0; h < t.length; h++) {
            while (q > 0 && t[q] != t[h]) {
               q = next[q - 1];
            }
            if (t[q] == t[h]) {
                q++;
            }
            next[h] = q;
        }
        for (int tt = 0, ss = 0; ss < s.length; ss++) {
            while (tt > 0 && t[tt] != s[ss]) {
                tt = next[tt - 1];
            }
            if (t[tt] == s[ss]) {
                tt++;
            }
            if (tt == t.length) {
                return ss - tt + 1;
            }

        }
        return -1;
    }