POJ 1287 Networking(最小生成树)

POJ 1287 Networking(最小生成树)

http://poj.org/problem?id=1287

题意:

给你一个N个点和M条边的无向图,要求最小生成树的权值.

分析:

最小生成树模板题,直接用kruskal模板即可.

AC代码:

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int maxn=1000+10;
const int maxm=150000+10;

struct Edge
{
    int u,v,dist;
    Edge(){}
    Edge(int u,int v,int d):u(u),v(v),dist(d){}
    bool operator<(const Edge &rhs)const
    {
        return dist<rhs.dist;
    }
};

struct Kruskal
{
    int n,m;
    Edge edges[maxm];
    int fa[maxn];
    int findset(int x){ return fa[x]==-1?x:fa[x]=findset(fa[x]); }

    void init(int n)
    {
        this->n=n;
        m=0;
        memset(fa,-1,sizeof(fa));
    }

    void AddEdge(int u,int v,int dist)
    {
        edges[m++]=Edge(u,v,dist);
    }

    int kruskal()
    {
        int sum=0,cnt=0;
        sort(edges,edges+m);

        for(int i=0;i<m;i++)
        {
            int u=edges[i].u, v=edges[i].v;
            if(findset(u) != findset(v))
            {
                fa[findset(u)] = findset(v);
                sum +=edges[i].dist;
                if(++cnt>=n-1) return sum;
            }
        }
        return -1;
    }
}KK;

int main()
{
    int n,m;
    while(scanf("%d",&n)==1&&n)
    {
        scanf("%d",&m);
        if(m==0) {printf("0\n"); continue;}
        KK.init(n);
        while(m--)
        {
            int u,v,d;
            scanf("%d%d%d",&u,&v,&d);
            KK.AddEdge(u,v,d);
        }
        printf("%d\n",KK.kruskal());
    }
    return 0;
}