HDU 3948 The Number of Palindromes

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 const int maxn = 100010;
 4 struct PalindromicTree{
 5     int son[maxn][26],fail[maxn],len[maxn],s[maxn];
 6     int tot,last,n;
 7     int newnode(int slen = 0){
 8         memset(son[tot],0,sizeof son[tot]);
 9         len[tot] = slen;
10         return tot++;
11     }
12     void init(){
13         tot = last = n = 0;
14         newnode(0);
15         newnode(-1);
16         fail[0] = fail[1] = 1;
17         s[n] = -1;
18     }
19     int getFail(int x){
20         while(s[n - len[x] -1] != s[n]) x = fail[x];
21         return x;
22     }
23     void extend(int c){
24         s[++n] = c;
25         int cur = getFail(last);
26         if(!son[cur][c]){
27             int x = newnode(len[cur] + 2);
28             fail[x] = son[getFail(fail[cur])][c];
29             son[cur][c] = x;
30         }
31         last = son[cur][c];
32     }
33 }pt;
34 char str[maxn];
35 int main(){
36     int kase,cs = 1;
37     scanf("%d",&kase);
38     while(kase--){
39         scanf("%s",str);
40         pt.init();
41         for(int i = 0; str[i]; ++i)
42             pt.extend(str[i] - ‘a‘);
43         printf("Case #%d: %d\n",cs++,pt.tot - 2);
44     }
45     return 0;
46 }