POJ3974 Palindrome

 1 /*by SilverN*/
 2 #include<iostream>
 3 #include<algorithm>
 4 #include<cstring>
 5 #include<cstdio>
 6 #include<cmath>
 7 using namespace std;
 8 const int mxn=1000100;
 9 char s[mxn],c[mxn<<1];
10 int len;
11 int p[mxn<<1];
12 void mana(){
13     int id=0,mx=0;
14     int i,j;
15     for(i=1;i<len;i++){
16         if(mx>i)p[i]=min(p[2*id-i],p[id]+id-i);
17         else p[i]=1;
18         while(c[i+p[i]]==c[i-p[i]])p[i]++;
19         if(p[i]+i>mx){
20             mx=p[i]+i;
21             id=i;
22         }
23     }
24     return;
25 }
26 int main(){
27     int cas=0;
28     while(scanf("%s",s)!=EOF){
29         if(s[0]==‘E‘)break;
30         int i,j;
31         c[0]=‘$‘;c[1]=‘#‘;
32         len=strlen(s);
33         for(i=0;i<len;i++){
34           c[i*2+2]=s[i];c[i*2+3]=‘#‘;
35         }
36         
37         len=len*2+2;
38         c[len]=‘%‘;
39         mana();
40         int ans=0;
41         for(i=0;i<len;i++)ans=max(ans,p[i]);
42         printf("Case %d: %d\n",++cas,ans-1);
43     }
44     return 0;
45 }