UVa 11631 - Dark roads

　　题目大意：政府为了减小开支决定关闭一些路灯，同时保证照亮的路能连接所有路口。

　　又是一个MST问题，Kruskal算法，不过数据规模比较大，又Submission Error了...扔这吧...

 1 #include <cstdio>
 2 #include <vector>
 3 #include <algorithm>
 4 using namespace std;
 5 typedef pair<int, int> ii;
 6 #define MAXN 200100
 7 
 8 int p[MAXN];
 9 
10 int find(int x)
11 {
12     return p[x] == x ? x : p[x]=find(p[x]);
13 }
14 
15 int main()
16 {
17 #ifdef LOCAL
18     freopen("in", "r", stdin);
19 #endif
20     int n, m;
21     while (scanf("%d%d", &n, &m) && (n || m))
22     {
23         int u, v, w;
24         int total_cost = 0;
25         vector<pair<int, ii> > EdgeList;
26         for (int i = 0; i < m; i++)
27         {
28             scanf("%d%d%d", &u, &v, &w);
29             total_cost += w;
30             EdgeList.push_back(make_pair(w, make_pair(u, v)));
31         }
32         sort(EdgeList.begin(), EdgeList.end());
33         for (int i = 0; i < n; i++)
34             p[i]= i;
35         int cost = 0;
36         for (int i = 0; i < EdgeList.size(); i++)
37         {
38             w = EdgeList[i].first;
39             u = EdgeList[i].second.first;
40             v = EdgeList[i].second.second;
41             int pu = find(u);
42             int pv = find(v);
43             if (pu != pv)
44             {
45                 cost += w;
46                 p[pv] = pu;
47             }
48         }
49         printf("%d\n", total_cost-cost);
50     }
51     return 0;
52 }
View Code

 

posted @ 2013-09-17 21:54  xiaobaibuhei  阅读(219)  评论(0)    收藏  举报