【HDOJ】3367 Pseudoforest

并查集。

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <cstdlib>
 4 
 5 #define MAXN 10005
 6 #define INF  0xffffff
 7 
 8 typedef struct {
 9     int c, s, e;
10 } edge_st;
11 
12 edge_st edges[100005];
13 int pre[MAXN];
14 int deg[MAXN];
15 int n, m, ans;
16 
17 int comp(const void *a, const void *b) {
18     return ((edge_st *)b)->c - ((edge_st *)a)->c;
19 }
20 
21 int find(int x) {
22     return x==pre[x] ? x:pre[x]=find(pre[x]);
23 }
24 
25 void merge(int i) {
26     int a, b;
27 
28     a = find(edges[i].s);
29     b = find(edges[i].e);
30     if (a != b) {
31         if (deg[a] == 0) {
32             pre[a] = b;
33             ans += edges[i].c;
34         } else if (deg[b] == 0) {
35             pre[b] = a;
36             ans += edges[i].c;
37         }
38     } else {
39         if (deg[a] == 0) {
40             ++deg[a];
41             ans += edges[i].c;
42         }
43     }
44 }
45 
46 int main() {
47     int i;
48 
49     while (scanf("%d %d", &n, &m)!=EOF && (n||m)) {
50         for (i=0; i<m; ++i)
51             scanf("%d %d %d", &edges[i].s, &edges[i].e, &edges[i].c);
52         qsort(edges, m, sizeof(edge_st), comp);
53         for (i=0; i<n; ++i)
54             pre[i] = i;
55         memset(deg, 0, sizeof(deg));
56         ans = 0;
57         for (i=0; i<m; ++i)
58             merge(i);
59         printf("%d\n", ans);
60     }
61 
62     return 0;
63 }

 

posted on 2014-06-20 23:46  Bombe  阅读(156)  评论(0)  编辑  收藏  举报

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