hdu 3367 Pseudoforest 最大生成树★

Posted 2020-10-13

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <vector>
 4 #include <algorithm>
 5 using namespace std;
 6 
 7 const int maxn = 100005;
 8 int n, m;
 9 struct node
10 {
11     int u, v, c;
12 }g[maxn];
13 long long ans;
14 int fa[maxn];
15 int ff[maxn];
16 int ee[maxn];
17 
18 bool cmp(node a, node b){
19     return a.c > b.c;
20 }
21 
22 void init(){
23     memset(ff, false, sizeof(ff));
24     memset(ee, false, sizeof(ee));
25     for (int i = 0; i < n; i++){
26         fa[i] = i;
27     }
28 }
29 
30 int find(int x){
31     if (x == fa[x])
32         return x;
33     else
34         return fa[x] = find(fa[x]);
35 }
36 
37 void Union(int x, int y, int z){
38     int a = find(x);
39     int b = find(y);
40     if (a == b){
41         if (ff[a])
42             return;
43         ans += z;
44         ff[a] = true;
45     }
46     else{
47         if (ff[a] && ff[b])
48             return;
49         ans += z;
50         fa[b] = a;
51         if (ff[a] || ff[b])
52             ff[a] = true;
53     }
54 }
55 
56 int main(){
57     while (~scanf("%d%d", &n, &m)){
58         if (n == 0 && m == 0)
59             break;
60         init();
61         int u, v, c;
62         for (int i = 0; i < m; i++){
63             scanf("%d%d%d", &u, &v, &c);
64             g[i].u = u;
65             g[i].v = v;
66             g[i].c = c;
67         }
68         //克鲁斯卡尔
69         sort(g, g + m, cmp);    //按边从小到大排列
70         ans = 0;
71         for (int i = 0; i < m; i++){
72             Union(g[i].u, g[i].v, g[i].c);
73         }
74         printf("%lld\n", ans);
75     }
76     //system("pause");
77     return 0;
78 }