hdu1863-畅通工程

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畅通工程

最小生成树，通过统计连通路的个数和总路数比较，来判断是否所有的路径都已经连通了，需要注意的是这里sum应该从1 开始，因为一开始就是从某一条路出发的

// File Name: hdu1863.cpp// Author: rudolf// Created Time: 2013年04月27日 星期六 15时21分31秒#include<vector>#include<list>#include<map>#include<set>#include<deque>#include<stack>#include<bitset>#include<algorithm>#include<functional>#include<numeric>#include<utility>#include<sstream>#include<iostream>#include<iomanip>#include<cstdio>#include<cmath>#include<cstdlib>#include<cstring>#include<ctime>using namespace std;const int maxn=10005;int fa[105];struct node{int x,y,value;}edge[maxn];int find( int x ){return fa[ x ] = x == fa[ x ]? x : find( fa[ x ] );}int cmp( const node a, const node b ){return a.value < b.value;}int main(){int m,n;int i;while(cin>>n>>m){if( n == 0 )break;for( i = 1; i <= m; i++ )fa[ i ] = i;for( i = 1; i <= n; i++ ){cin>>edge[i].x>>edge[i].y>>edge[i].value;}sort( edge + 1 , edge + n + 1, cmp );int ans = 0;int sum=1;for( i = 1;i <= n; i++ ){int x1 = find( edge[ i ].x );int x2 = find( edge[ i ].y );if( x1 != x2 ){fa[ x1 ] = x2;ans += edge[ i ].value;sum++;}}if( sum == m )cout<<ans<<endl;elsecout<<"?"<<endl;}return 0;}