HDU3068 最长回文

#include<cstdio>
const int N=220005;
char a
,s
;
int p
;
int len,pos,mx,Len,ans;
inline int max(const int &a,const int &b){return a>b?a:b;}
inline int min(const int &a,const int &b){return a<b?a:b;}
int main()
{
while(scanf("%s",s)==1)
{
Len=0;
for(int i=0;s[i];i++)
a[++Len]='#',a[++Len]=s[i];
a[Len+1]=a[Len+2]='#',a[0]='$';
ans=mx=pos=0;
for(int i=1;i<=Len;i++)
{
if(mx>i) p[i]=min(p[2*pos-i],mx-i);
else p[i]=1;
while(a[i+p[i]]==a[i-p[i]]) p[i]++;
if(i+p[i]>mx) mx=i+p[i],pos=i;
ans=max(ans,p[i]-1);
}
printf("%d\n",ans);
}
return 0;
}