UVa 11631

　　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...

#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;
typedef pair<int, int> ii;
#define MAXN 200100

int p[MAXN];

int find(int x)
{
    return p[x] == x ? x : p[x]=find(p[x]);
}

int main()
{
#ifdef LOCAL
    freopen("in", "r", stdin);
#endif
    int n, m;
    while (scanf("%d%d", &n, &m) && (n || m))
    {
        int u, v, w;
        int total_cost = 0;
        vector<pair<int, ii> > EdgeList;
        for (int i = 0; i < m; i++)
        {
            scanf("%d%d%d", &u, &v, &w);
            total_cost += w;
            EdgeList.push_back(make_pair(w, make_pair(u, v)));
        }
        sort(EdgeList.begin(), EdgeList.end());
        for (int i = 0; i < n; i++)
            p[i]= i;
        int cost = 0;
        for (int i = 0; i < EdgeList.size(); i++)
        {
            w = EdgeList[i].first;
            u = EdgeList[i].second.first;
            v = EdgeList[i].second.second;
            int pu = find(u);
            int pv = find(v);
            if (pu != pv)
            {
                cost += w;
                p[pv] = pu;
            }
        }
        printf("%d
", total_cost-cost);
    }
    return 0;
}