Manacher 代码贴贴

#include<bits/stdc++.h>
using namespace std;
const int N=1.1e7+5;
char rS[N];
char S[N<<1];
int P[N<<1],n;
void init(){
	n=strlen(rS);
	int k=0;
	S[k++]='$';S[k++]='#';
	for(int i=0;i<n;i++){
		S[k++]=rS[i];
		S[k++]='#';
	}
	S[k++]='&';
	n=k;
}
int manacher(){
	int ans=1,mx=0,mxid=0;
	for(int i=1;i<n;i++){
		if(i<mx)P[i]=min(mx-i,P[2*mxid-i]);
		else P[i]=1;
		while(S[i+P[i]]==S[i-P[i]])P[i]++;
		if(P[i]+i>mx)mx=P[i]+i,mxid=i;
		ans=max(ans,P[i]);
	}
	return ans-1;
}
signed main(){
	scanf("%s",rS);
	init();
	printf("%d",manacher());
	return 0;
}