POJ 2377

 #include<stdio.h>
 #define MAXN 1005
 #include<iostream>
 #include<algorithm>
 #define inf 10000000
 using namespace std;
 int _m[MAXN][MAXN];
 int low_cost[MAXN];
 int pre[MAXN];
 unsigned prime(int n);
 int DFS(int i,int sum,int p);
 bool mark[MAXN];
 int main()
 {
     //freopen("acm.acm","r",stdin);
     int p;
     int edge;
     unsigned tem;
     int i;
     int j;
     int u;
     int v;
     while(cin>>p>>edge)
     {
         memset(mark,false,sizeof(mark));
         for(i = ; i < p; ++ i)
         {
             for(j = ; j < p; ++ j)
                 _m[i][j] = inf;
         }
         for(i = ; i < edge; ++ i)
         {
             cin>>u>>v;
             -- u;
             -- v;
             cin>>tem;
             if(_m[u][v] == inf)
             {
                 _m[u][v] = tem;
                 _m[u][v] *= -;
                 _m[v][u] = _m[u][v];
             }
             else
                 if(tem > _m[u][v]*(-))
                 {
                     _m[u][v] = tem;
                     _m[u][v] *= -;
                     _m[v][u] = _m[u][v];
                 }
         }
         mark[] = true;
         tem = -prime(p);
         if(DFS(,,p) == p)
             cout<<tem<<endl;
         else
             cout<<-<<endl;
     }
 }
 int DFS(int i,int sum,int n)
 {
     int j;
     for(j = ; j < n; ++ j)
     {
         if(i != j && _m[i][j] != inf && !mark[j])
         {
             mark[j] = true;
             sum = DFS(j,sum+,n);
         }
     }
     return sum;
 }
 unsigned prime(int n)
 {
     int i;
     int j;
     int k;
     unsigned sum = ;
     int min;
     for(i = ; i < n; ++ i)
     {
         low_cost[i] = _m[][i];
         pre[i] = ;
     }
     for(i = ; i < n; ++ i)
     {
         min = inf;
         for(j = ; j < n; ++ j)
         {
             if(low_cost[j]&&low_cost[j] < min)
             {
                 k = j;
                 min = low_cost[j];
             }
         }
         sum += low_cost[k];
         low_cost[k] = ;
         for(j = ; j < n; ++ j)
         {
             if(_m[k][j] < low_cost[j] && low_cost[j])
             {
                 low_cost[j] = _m[k][j];
                 pre[j] = k;
             }
         }
     }
     return sum;
 }