找字符串的最短循环节
1. kmp
#include <bits/stdc++.h>
using namespace std ;
const int N=1e6+1;
char a[N];
int n,p[N];
void init(){
int i,j=0;
for(i=1;i<n;i++){
while(j>0&&a[i+1]!=a[j+1]) j=p[j];
if(a[i+1]==a[j+1]) j++;
p[i+1]=j;
}
}
int main(){
while(cin>>a+1,a[1]!='.'){
n=strlen(a+1);
init();
if(n%(n-p[n])) cout<<1<<endl;
else cout<<n/(n-p[n])<<endl;
}
}
2. Hash
#include<iostream> #include <algorithm> #include <cstring> using namespace std; #define int long long const int N=1e6+5; char a[N]; int n; int h[N],pow[N]; int bas=29; int f2(int l,int r){ return h[r]-h[l-1]*pow[r-l+1]; } void solve(){ for(int i=1;i<=n;i++){ if(n%i==0&&f2(i+1,n)==f2(1,n-i)){ cout<<n/i<<endl;return; } } cout<<1<<endl; } signed main(){ pow[0]=1; for(int i=1;i<=1e6;i++) pow[i]=bas*pow[i-1]; while(cin>>a+1,a[1]!='.'){ n=strlen(a+1); for(int i=1;i<=n;i++) h[i]=h[i-1]*bas+a[i]; solve(); } }