【HDOJ】2988 Dark roads

最小生成树。

 /*  */
 #include <iostream>
 #include <string>
 #include <map>
 #include <queue>
 #include <set>
 #include <stack>
 #include <vector>
 #include <deque>
 #include <algorithm>
 #include <cstdio>
 #include <cmath>
 #include <ctime>
 #include <cstring>
 #include <climits>
 #include <cctype>
 #include <cassert>
 using namespace std;

 #define rep(i, a, n)     for (int i=a;i<n;++i)
 #define per(i, a, n)     for (int i=n-1;i>=a;--i)
 #define pb                 push_back
 #define mp                 make_pair
 #define all(x)             (x).begin(),(x).end()
 #define SZ(x)             ((int)(x).size())
 #define lson            l, mid, rt<<1
 #define rson            mid+1, r, rt<<1|1

 typedef struct Edge_t {
     int u, v, w;
     friend bool operator <(const Edge_t &a, const Edge_t &b) {
         return a.w < b.w;
     }
 } Edge_t;

 const int maxn = ;
 int pre[maxn];
 Edge_t E[maxn];

 int find(int x) {
     if (x == pre[x])
         return x;
     return pre[x] = find(pre[x]);
 }

 int main() {
     int i, j, k;
     int n, m;
     int ans;
     int fu, fv;

     #ifndef ONLINE_JUDGE
         freopen("data.in", "r", stdin);
         freopen("data.out", "w", stdout);
     #endif

     while (scanf("%d %d", &n, &m)!=EOF && (n||m)) {
         for (i=; i<n; ++i)
             pre[i] = i;
         for (i=; i<m; ++i)
             scanf("%d %d %d", &E[i].u, &E[i].v, &E[i].w);
         sort(E, E+m);
         ans = ;
         for (i=; i<m; ++i) {
             fu = find(E[i].u);
             fv = find(E[i].v);
             if (fu != fv)
                 pre[fu] = fv;
             else
                 ans += E[i].w;
         }
         printf("%d\n", ans);
     }

     #ifndef ONLINE_JUDGE
         printf("time = %d.\n", (int)clock());
     #endif

     return ;
 }