大水题，不过考试时我想到的是KMP

#include
     
      using namespace std;const int maxn=1e6+7;char s1[maxn],s2[maxn];bool flag1,flag2;int fail[maxn];int fail1[maxn];int len1,len2;char test[maxn];char test1[maxn];int suma[maxn];int sumc[maxn];int sum1a[maxn];int sum1c[maxn];int ans1,ans2;void pre(){    fail[1]=0;    fail[2]=0;    fail1[1]=0;    fail1[2]=0;}void kmp1(){    int ans=0,j=0;    int l1=strlen(test+1);    for(int i=1;i<=len1;i++)    {        while(j>0&&test[j+1]!=s1[i]) j=fail[j];        if(test[j+1]==s1[i]) j++;        if(j==l1)         {            ans++;            suma[ans]=i-l1+1;           }    }    ans1=ans;}void kmp2(){    int ans=0,j=0;    int l2=strlen(test1+1);    for(int i=1;i<=len1;i++)    {        while(j>0&&test1[j+1]!=s1[i]) j=fail1[j];        if(test1[j+1]==s1[i]) j++;        if(j==l2)        {            ans++;            sum1c[ans]=i-l2+1;        }    }    ans2=ans;}bool check(){    for(int i=1;i<=ans1;i++)    {        for(int j=1;j<=ans2;j++)        {            if(abs(suma[i]-sum1c[j])>1){                return true;            }         }    }    return false;}int main(){    while(scanf("%s",s1+1)!=EOF)    {        memset(fail1,0,sizeof(fail1));        memset(fail,0,sizeof(fail));        len1=strlen(s1+1);        test[1]='A';        test[2]='C';        test1[1]='C';        test1[2]='A';        pre();        kmp1();        kmp2();        if(check()) printf("YES\n");        else printf("NO\n");    }    return 0;}