hdu 2594-Simpsons’ Hidden Talents（KMP）

#include <map>
#include <set>
#include <list>
#include <cmath>
#include <queue>
#include <stack>
#include <cstdio>
#include <vector>
#include <string>
#include <cctype>
#include <complex>
#include <cassert>
#include <utility>
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <algorithm>
using namespace std;
typedef pair<int,int> PII;
typedef long long ll;
#define lson l,m,rt<<1
#define pi acos(-1.0)
#define rson m+1,r,rt<<11
#define All 1,N,1
#define N 50010
#define read freopen("in.txt", "r", stdin)
const ll  INFll = 0x3f3f3f3f3f3f3f3fLL;
const int INF= 0x7ffffff;
const int mod =  1000000007;
char a[N*2],b[N];
int f[N*2];
void getnext(int n){
    int i=0,j=-1;
    f[0]=-1;
    while(i<n){
        if(j==-1||a[i]==a[j]){
            i++;
            j++;
            f[i]=j;
        }
        else
            j=f[j];
    }
}
void solve(){
    int len1=strlen(a);
    int len2=strlen(b);
    strcat(a,b);
     int tmp=len1+len2;
    getnext(tmp);
    //必须是两串的子串
    while(f[tmp]>len1)tmp=f[tmp];
    while(f[tmp]>len2)tmp=f[tmp];
    if(f[tmp]==0)
        printf("0\n");
    else{
        for(int i=0;i<f[tmp];++i)
            printf("%c",a[i]);
        printf(" %d\n",f[tmp]);
    }
}
int main()
{
    while(~scanf("%s%s",a,b)){
        solve();
    }
return 0;
}