hdu 1869 floyd

 1 #include <algorithm>
 2 #include <iostream>
 3 #include <cstring>
 4 #include <cstdio>
 5 using namespace std;
 6 
 7 const int INF = 999999;
 8 const int N = 100;
 9 int g[N][N];
10 int n, m;
11 
12 void init()
13 {
14     for ( int i = 0; i < n; i++ )
15     {
16         for ( int j = 0; j < n; j++ )
17         {
18             g[i][j] = INF;
19         }
20     }
21 }
22 
23 void floyd()
24 {
25     for ( int k = 0; k < n; k++ )
26     {
27         for ( int i = 0; i < n; i++ )
28         {
29             for ( int j = 0; j < n; j++ )
30             {
31                 if ( g[i][k] + g[k][j] < g[i][j] )
32                 {
33                     g[i][j] = g[i][k] + g[k][j];
34                 }
35             }
36         }
37     }
38 }
39 
40 void judge()
41 {
42     for ( int i = 0; i < n; i++ )
43     {
44         for ( int j = 0; j < n; j++ )
45         {
46             if ( i == j ) continue;
47             if ( g[i][j] > 7 )
48             {
49                 printf("No\n");
50                 return ;
51             }
52         }
53     }
54     printf("Yes\n");
55 }
56 
57 int main ()
58 {
59     while ( scanf("%d%d", &n, &m) != EOF )
60     {
61         init();
62         while ( m-- )
63         {
64             int a, b;
65             scanf("%d%d", &a, &b);
66             g[a][b] = g[b][a] = 1;
67         }
68         floyd();
69         judge();
70     }
71     return 0;
72 }