【HDU1301】Jungle Roads（MST基础题）

 1 #include <iostream>
 2 #include <cstring>
 3 #include <cstdlib>
 4 #include <cstdio>
 5 #include <cmath>
 6 #include <cctype>
 7 #include <algorithm>
 8 #include <numeric>
 9 
10 #define typec int
11 using namespace std;
12 
13 const typec inf = 0xffff;
14 const int V = 35;
15 int vis[V]; typec lowc[V];
16 int Map[V][V];
17 
18 typec prim (typec cost[][V], int n) {
19     int i, j, p;
20     typec minc, res = 0;
21     memset(vis, 0, sizeof (vis));
22     vis[0] = 1;
23     for (i = 1; i < n; ++ i) lowc[i] = cost[0][i];
24     for (i = 1; i < n; ++ i) {
25         minc = inf; p = -1;
26         for (j = 0 ; j < n; ++ j) {
27             if ( 0 == vis[j] && minc > lowc[j]) {
28                 minc = lowc[j]; p = j;
29             }
30         }
31         if (inf == minc) return -1;
32         res += minc; vis[p] = 1;
33         for (j = 0 ; j < n; ++ j) {
34             if (0 == vis[j] && lowc[j] > cost[p][j]) {
35                 lowc[j] = cost[p][j];
36             }
37         }
38     }
39     return res;
40 }
41 
42 
43 int main () {
44     int n;
45     while (~scanf("%d", &n)) {
46         if (n == 0) break;
47         for (int i = 0 ; i < n; ++ i) {
48             for (int j = 0 ;j < n; ++ j) {
49                 if (i == j) Map[i][j] = 0;
50                 else Map[i][j] = inf;
51             }
52         }
53 
54         for (int i = 0 ; i < n - 1; ++ i) {
55             char s_c; int e_n;
56             cin >> s_c >> e_n;
57             for (int j = 0 ; j < e_n; ++ j) {
58                 char e_c; int w;
59                 cin >> e_c >> w;
60                 Map[s_c - ‘A‘][e_c - ‘A‘] = Map[e_c - ‘A‘][s_c - ‘A‘] = min(Map[s_c - ‘A‘][e_c - ‘A‘], w);
61             }
62         }
63 
64         cout << prim(Map, n) << endl;
65     }
66     return 0;
67 }