pku2941 Homogeneous Squares

http://poj.org/problem?id=2941

随机算法

 1 #include <stdio.h>
 2 #include <stdlib.h>
 3 #include <time.h>
 4 
 5 int a[1234][1234], n, stack[1234];
 6 
 7 int check()
 8 {
 9     int i, j, temp, sum1 = 0, sum2, m;
10     for(i=1; i<=n; i++)
11     {
12         sum1 += a[i][i];
13         stack[i] = i;
14     }
15     m = 300000;
16     while(m--)
17     {
18         sum2 = sum1;
19         j = rand()%n+1;
20         sum2 -= (a[1][stack[1]] + a[j][stack[j]]);
21         temp = stack[j];
22         stack[j] = stack[1];
23         stack[1] = temp;
24         sum2 += (a[1][stack[1]] + a[j][stack[j]]);
25         if(sum1 != sum2)
26         {
27             return 0;
28         }
29     }
30     return 1;
31 }
32 
33 int main()
34 {
35     int i, j;
36     while(scanf("%d", &n), n)
37     {
38         for(i=1; i<=n; i++)
39         {
40             for(j=1; j<=n; j++)
41             {
42                 scanf("%d", &a[i][j]);
43             }
44         }
45         printf(check()? "homogeneous\n": "not homogeneous\n");
46     }
47     return 0;
48 }

 

posted @ 2013-03-12 10:31  Yuan1991  阅读(181)  评论(0)  编辑  收藏  举报