HDU 3068 回文串--Manacher

//2009 Multi-University Training Contest 16 - Host by NIT
//最长回文
#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

const int maxn = 100000 + 10;

char Ma[maxn*2];
int Mp[maxn*2];

void Manacher(char s[],int len)
{
int l=0;
Ma[l++]='$';
Ma[l++]='#';
for(int i=0;i<len;i++)
{
Ma[l++]=s[i];
Ma[l++]='#';
}
Ma[l]=0;
int mx=0,id=0;
for(int i=0;i<l;i++)
{
Mp[i]=mx>i?min(Mp[2*id-i],mx-i):1;
while(Ma[i+Mp[i]]==Ma[i-Mp[i]]) Mp[i]++;
if(i+Mp[i]>mx)
{
mx=i+Mp[i];
id=i;
}
}
}

char s[maxn];

int main()
{
while(~scanf("%s",s))
{
int len=strlen(s);
Manacher(s,len);
int ans=0;
for(int i=0;i<2*len+2;i++)
ans=max(ans,Mp[i]-1);
printf("%d\n",ans);
}
return 0;
}