POJ 3974 Palindrome

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <climits>
 7 #include <vector>
 8 #include <queue>
 9 #include <cstdlib>
10 #include <string>
11 #include <set>
12 #include <stack>
13 #define LL long long
14 #define pii pair<int,int>
15 #define INF 0x3f3f3f3f
16 using namespace std;
17 const int maxn = 2000100;
18 char tmp[maxn],str[maxn];
19 int p[maxn];
20 void manacher(char *s,int n){
21     int maxlen = 0,id;
22     id = p[0] = 0;
23     for(int i = 1; i < n; i++){
24         if(p[id]+id > i) p[i] = min(p[2*id-i],p[id]+id-i);
25         else p[i] = 1;
26         while(i-p[i] >= 0 && s[i-p[i]] == s[i+p[i]]) p[i]++;
27         if(id+p[id] < i+p[i]) id = i;
28         if(p[i] > maxlen) maxlen = p[i];
29     }
30     printf("%d\n",maxlen-1);
31 }
32 int main() {
33     int i,j,cs = 1;
34     while(~scanf("%s",tmp)){
35         if(!strcmp(tmp,"END")) break;
36         for(i = j = 0; tmp[i]; i++ ,j += 2){
37             str[j] = ‘#‘;
38             str[j+1] = tmp[i];
39         }
40         str[j++] = ‘#‘;
41         str[j] = ‘\0‘;
42         printf("Case %d: ",cs++);
43         manacher(str,j);
44     }
45     return 0;
46 }