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POJ 3974  

网上看到的O(n)的方法，Manacher算法，记录一下

 1 #include <stdio.h>
 2 #include <stdlib.h>
 3 #include <string.h>
 4 
 5 #define MAX(a,b) (a>b?a:b)
 6 #define MIN(a,b) (a<b?a:b)
 7 
 8 #define M 1000000
 9 #define N (M+1)*2
10 
11 char input[M+1];
12 char str[N];
13 int p[N];
14 
15 int main()
16 {
17     int n;
18     int count = 1;
19     int i,j;
20     int mx = 0;
21     int id;
22     int max;
23 
24     while(scanf("%s",input) && !(input[0] == 'E' && input[1] == 'N' && input[2] == 'D'))
25     {
26         max = 0;
27         mx = 0;
28         n = strlen(input);
29         str[0] = '$';
30         str[1] = '#';
31         for(i=0; i<n; i++)
32         {
33             str[2*i+2] = input[i]; 
34             str[2*i+3] = '#';
35         }
36         n = 2*n+2;
37         str[n] = '\0';
38 
39         for(i=1;i<n;i++)
40         {
41             if(mx > i)
42                 p[i] = MIN(p[2*id-i], mx-i);
43             else
44                 p[i] = 1;
45 
46             for(;str[i+p[i]] == str[i-p[i]]; p[i]++) ;
47             if(p[i] + i > mx)
48             {
49                 mx = p[i] + i;
50                 id = i;
51                 max = MAX(max,p[i]);
52             }
53             
54         }
55         printf("Case %d: %d\n", count++, max-1);
56     }
57 
58     return 0;
59 }
posted @ 2012-05-07 14:50  无啦啦  阅读(116)  评论(0)    收藏  举报