3620: 似乎在梦中见过的样子 KMP

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
int n,ans,k;
char s[20005];
int next[20005];
inline void KMP(int p)
{
for (int i=1;i<=n;i++)
next[i]=p-1;
int j=p-1;
for (int i=p+1;i<=n;i++)
{
while (j!=p-1&&s[j+1]!=s[i]) j=next[j];
if (s[j+1]==s[i]) j++;
next[i]=j;
}
j=p-1;
for (int i=p+1;i<=n;i++)
{
while (j!=p-1&&s[j+1]!=s[i]) j=next[j];
if (s[j+1]==s[i]) j++;
while ((j-p+1)*2>=(i-p+1)) j=next[j];
if (j-p+1>=k) ans++;
}
}
int main()
{
scanf("%s%d",s+1,&k);
n=strlen(s+1);
for (int i=1;i<=n;i++)
KMP(i);
cout << ans << endl;
}