亲和串（HDU2203）

http://acm.hdu.edu.cn/showproblem.php?pid=2203

题目意思很简单，求s1串所构成的环中是否有s2这个串     

用CMP参考http://s.acmore.net/show_article/show/44

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <iostream>
#include <stack>
#include <set>
#include <queue>
#define MAX(a,b) (a) > (b)? (a):(b)
#define MIN(a,b) (a) < (b)? (a):(b)
#define mem(a) memset(a,0,sizeof(a))
#define INF 1000000007
#define MAXN 100005
using namespace std;

char a[2*MAXN],b[MAXN];
int next[MAXN];

void get_next()
{
    next[0]=-1;
    int key = -1;
    int index = 0;
    int len =strlen(b);
    while(index < len-1)
    {
        if(key == -1 || b[index] == b[key])
        {
            next[++index] = ++key;
        }
        else{
            key = next[key];
        }
    }
}

int KMP()
{
    int A=0,B=0;
    int len1 = strlen(a);
    int len2 = strlen(b);
    while(A<len1 && B<len2)
    {
        if(B==-1 || a[A] == b[B])
        {
            A++;B++;
        }
        else
        {
            B=next[B];
        }
    }
    if(B >= len2)return 1;
    return 0;
}

int main()
{
    while(~scanf("%s%s",a,b))
    {
        int len = strlen(a);
        for(int i=0; i<len; i++)
        {
            a[len+i] = a[i];
        }
        get_next();
        printf("%s\n",KMP()?"yes":"no");
    }
    return 0;
}