#51nod上刷topcoder

 1 #include <bits/stdc++.h>
 2 
 3 const int N = 55;
 4 const int INF = 0x3f3f3f3f;
 5 
 6 char s[N];
 7 int mp[N][N], fa[N], n;
 8 
 9 int getfa(int x) {
10     return x == fa[x] ? x : fa[x] = getfa(fa[x]);
11 }
12 
13 void unit(int x, int y) {
14     x = getfa(x), y = getfa(y);
15     fa[x] = y;
16 }
17 
18 void floyd() {
19     for (int k = 1; k <= n; k++)
20         for (int i = 1; i <= n; i++)
21             for (int j = 1; j <= n; j++)
22                 mp[i][j] = std::min(mp[i][j], mp[i][k] + mp[k][j]);
23 }
24 
25 int main() {
26     int T;
27     scanf("%d", &T);
28     while (T--) {
29         int d;
30         scanf("%d%d", &n, &d);
31         for (int i = 1; i <= n; i++) fa[i] = i;
32         for (int i = 1; i <= n; i++) {
33             scanf("%s", s + 1);
34             for (int j = 1; j <= n; j++) {
35                 if (s[j] == ‘Y‘ && i != j)
36                     mp[i][j] = d, unit(i, j);
37                 else if (i != j)
38                     mp[i][j] = INF;
39                 else 
40                     mp[i][j] = 0;
41             }
42         }
43         int cnt = 0;
44         for (int i = 1; i <= n; i++)
45             if (getfa(i) == i) cnt++;
46         if (cnt > 1) {
47             puts("-1");
48             continue;
49         }
50         floyd();
51         int ans = 0;
52         for (int i = 1; i <= n; i++)
53             for (int j = 1; j <= n; j++)
54                 if (mp[i][j] < INF) 
55                     ans = std::max(ans, mp[i][j]);
56         printf("%d\n", ans);
57     }
58     return 0;
59 }