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参考题目:洛谷P3085
解析:
关于 的讲解目前网上有很多啊,画图手残党可能要很久以后才会更新。
代码:
#include<bits/stdc++.h>
using namespace std;
#define re register
#define ll long long
#define gc getchar
#define pc putchar
#define cs const
#define st static
char s[22000001];
int R[22000001];
char c[22000001];
int len;
inline
void manacher(){
int maxr=0,mid=0;
for(int re i=1;i<=len;++i){
if(maxr>i)R[i]=min(R[(mid<<1)-i],maxr-i-1);
else R[i]=0;
while(s[i-R[i]-1]==s[i+R[i]+1])++R[i];
if(i+R[i]+1>maxr)mid=i,maxr=i+R[i]+1;
}
}
signed main(){
scanf("%s",c+1);
len=strlen(c+1);
s[0]='$';
s[1]='#';
for(int re i=1;i<=len;++i){
s[i<<1]=c[i];
s[i<<1|1]='#';
}
len=len<<1|1;
manacher();
int ans=0;
for(int re i=1;i<=len;++i){
ans=max(R[i],ans);
}
cout<<ans;
return 0;
}