manecher

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
char a[1000001],s[2000005];
int n,l,p[2000005],ans,k=-1,m=1;
void manacher()
{
    int pos=0,id=0,x=0;
    for(int i=2;i<=n-2;i++)
    {
        if(pos<=i) x=1;
        else x=min(p[2*id-i],pos-i);
        while(s[i+x]==s[i-x]) x++;
        p[i]=x;
        if(i+x>pos) 
        {
            pos=i+x;
            id=i;
        }
    }
}
int main()
{
    while(cin>>a)
    {
        if(a[0]=='E') return 0;
        ans=0,n=0;
        l=strlen(a);
        s[n++]='%';
        for(int i=0;i<l;i++)
        {
            s[n++]='#';
            s[n++]=a[i];
        }
        s[n++]='#';
        s[n]='@';
        manacher();
        for(int i=1;i<=n;i++) 
         if(ans<p[i]) 
         {
             ans=p[i];
             k=i;
         }
        if(s[k]=='#') printf("Case %d: %d
",m++,ans/2*2);
        else printf("Case %d: %d
",m++,ans/2*2-1);    
    }

}
原文地址:https://www.cnblogs.com/TheRoadToTheGold/p/6286728.html