Hdu 3068 最长回文（Manacher模版题）

Posted 2020-10-23 采蘑菇的小西佬

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
const int N=220010;
using namespace std;
char str[N];
char tmp[N];
int len[N];
int init(){
    tmp[0]=‘$‘;
    int i=0,nlen=1;
    while(str[i]!=‘\0‘){
        tmp[nlen++]=‘#‘;
        tmp[nlen++]=str[i];
        i++;
    }
    tmp[nlen++]=‘#‘;
　　 tmp[nlen++]=‘$‘;
    tmp[nlen]=0;
    return nlen;
}
int Manacher(int x){
    int mx=0,ans=1,pos=0;
    for(int i=0;i<x;i++){
        len[i]=mx>i?min(mx-i,len[2*pos-i]):1;
        while(tmp[i-len[i]]==tmp[i+len[i]])len[i]++;
        if(len[i]+i>mx){
            mx=len[i]+i;
            pos=i;
        }
        ans=max(ans,len[i]);
    }
    return ans-1;
}
int main(){
    while(~scanf("%s",str)){
        memset(len,0,sizeof(len));
        int x=init();
        printf("%d\n",Manacher(x));
    }
    return 0;
}