模板—字符串—Manacher

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
#define N 11000010
int len[N<<1],n,ans; char str[N],s[N<<1]; long long sum;
namespace Manacher
{
int init(char *str)
{
int n=strlen(str);
for(int i=1,j=0;i<=2*n;j++,i+=2)
s[i]='#',s[i+1]=str[j];
s[0]='$',s[2*n+1]='#',s[2*n+2]='@',s[2*n+3]='\0';
return 2*n+1;
}
void manacher(int l,int r)
{
int mx=0,p=0;
for(int i=l;i<=r;i++)
{
if(mx>i) len[i]=min(mx-i,len[2*p-i]);
else len[i]=1;
while(s[i-len[i]]==s[i+len[i]]) len[i]++;
if(len[i]+i>mx) mx=len[i]+i,p=i;
}
}
}
using namespace Manacher;
int main()
{
scanf("%s",str),n=init(str),manacher(1,n);
for(int i=1;i<=n;i++) ans=max(ans,len[i]/2*2-(i%2==0)),sum+=len[i]/2;
printf("%d %lld\n",ans,sum);
}