KMP应用http://acm.hdu.edu.cn/showproblem.php?pid=2594

riemann与marjorie拼接后riemannmarjorie前缀与后缀公共部分为 rie 长度为 3（即next[l] = next[14]的值，l为拼接后的长度）
但：aaaa与aa拼接后aaaaaa，next[l]不是结果，所以在aaaa和aa间加“#”，即aaaa#aa；
#include<stdio.h>
#include<string.h>
#include<math.h>
#include<stdlib.h>
#define N 50010

char s1[2 * N], s2[N];
int next[2 * N];

void GetNext(char s[])
{
    int k = -1, j = 0, l = strlen(s);
    next[0] = -1;
    while(j < l)
    {
        if(k == -1 || s[j] == s[k])
        {
            k++;
            j++;
            next[j] = k;
        }
        else
            k = next[k];
    }
}

int main()
{
    int l1, l2, i, l;
    while(scanf("%s%s", s1, s2) != EOF)
    {
        l1 = strlen(s1);
        l2 = strlen(s2);
        s1[l1] = '#';
        s1[l1 + 1] = '\0';
        strcat(s1, s2);
        GetNext(s1);
        l = l1 + l2;

        if(next[l + 1] == 0)
            printf("0\n");
        else
        {
            for(i = 0 ; i < next[l + 1] ; i++)
                printf("%c", s1[i]);
            printf(" %d\n", next[l + 1]);
        }
    }
    return 0;
}