KMP算法

public class Main {

    public static void main(String[] args) {
        char s[] = "ababca12341234fgdf".toCharArray();
        char t[] = "3412".toCharArray();
        int x = search(s, t);
        System.out.println(x);
    }

    private static int[] next(char[] pattern) {
        int[] result = new int[pattern.length];
        result[0] = -1;
        result[1] = 0;

        int i = 2;
        while (i < pattern.length) {
            if ((pattern[i - 1] == pattern[result[i - 1]])) {
                result[i] = result[i - 1] + 1;
            } else {
                result[i] = 0;
            }
            i++;
        }
        return result;
    }

    private static int search(char[] s, char[] t) {
        int i = 0, j = 0;
        int[] next = next(t);

        while (i < s.length) {
            if (s[i] == t[j]) {
                i++;
                j++;
                if (j == t.length) {
                    return i - j;
                }
            } else {
                j = next[j];
                if (j == -1) {
                    j++;
                    i++;
                }
            }
        }
        return -1;
    }
}