【HDU1233】还是畅通工程（MST基础题）

 1 #include <iostream>
 2 #include <cstring>
 3 #include <cstdio>
 4 #include <cmath>
 5 #include <cctype>
 6 #include <algorithm>
 7 #include <numeric>
 8 
 9 #define typec int
10 using namespace std;
11 
12 const int V = 105;
13 const int inf = 0xffff;
14 int vis[V]; typec lowc[V], Map[V][V];
15 
16 typec prim (typec cost[][V], int n) {
17     int i, j, p;
18     typec minc, res = 0;
19     memset(vis, 0, sizeof(vis));
20     vis[0] = 1;
21     for (int i = 1; i < n; ++ i) lowc[i] = cost[0][i];
22     for (int i = 1; i < n; ++ i) {
23         minc = inf; p = -1;
24         for (j = 0; j < n; ++ j) {
25             if (0 == vis[j] && minc > lowc[j]) {
26                 minc = lowc[j]; p = j;
27             }
28         }
29         if (inf == minc) return -1;
30         res += minc; vis[p] = 1;
31         for (j = 0; j < n; ++ j) {
32             if (0 == vis[j] && lowc[j] > cost[p][j])
33             lowc[j] = cost[p][j];
34         }
35     }
36     return res;
37 }
38 
39 int main () {
40     int n;
41     while (~scanf("%d", &n) && n) {
42         for (int i = 0; i < V; ++ i) {
43             for (int j = 0; j < V; ++ j) {
44                 if (i == j) Map[i][j] = 0;
45                     else Map[i][j] = inf;
46             }
47         }
48         for (int i = 0; i < n * (n - 1) / 2; ++i) {
49             int x, y, c; scanf("%d%d%d", &x, &y, &c);
50             if (x == y) continue;
51             Map[x - 1][y - 1] = Map[y - 1][x - 1] = min(Map[x - 1][y - 1], c);
52         }
53         cout << prim(Map, n) << endl;
54     }
55     return 0;
56 }