题解：将原来的串扩展为两倍，然后用KMP匹配。

#include <cstdio> #include <cstring>char str[200005],pat[100005];int next[100005],N,M;void getnext(){    int i=1,j=0;next[1]=0;	  while(i<M){		    if(j==0||pat[i]==pat[j])next[++i]=++j;		    else j=next[j];	  }}int KMP(){	  int i=0,j=0;	  while(i<=2*N&&j<=M){		    if(j==0||str[i]==pat[j])i++,j++;		    else j=next[j];	  }if(j>M)return 1; return 0;}int main(){    while(scanf("%s%s",str+1,pat+1)!=EOF){		    str[0]=pat[0]=‘#‘;		    N=strlen(str)-1; M=strlen(pat)-1;		    if(N<M){printf("no\n");continue;}		    for(int i=1;i<=N;i++)str[i+N]=str[i];		    str[2*N+1]=‘\0‘;getnext();	     	printf(KMP()?"yes\n":"no\n");	  }return 0;}