POJ 1258 Agri-Net(最小生成树)

POJ 1258 Agri-Net(最小生成树)

http://poj.org/problem?id=1258

题意:

给你一个N顶点的无向图的距离邻接矩阵,问你使得整个图连通的最小边长和是多少?

分析:

最小生成树入门题,直接kruskal模板.

AC代码:

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int maxn =100+10;
const int maxm=10000+10;

struct Edge
{
    int u,v,dist;
    Edge(){}
    Edge(int u,int v,int dist):u(u),v(v),dist(dist){}
    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;
    while(scanf("%d",&n)==1)
    {
        KK.init(n);
        for(int i=0;i<n;i++)
        for(int j=0;j<n;j++)
        {
            int x;
            scanf("%d",&x);
            if(i<j) KK.AddEdge(i,j,x);
        }
        printf("%d\n",KK.kruskal());
    }
    return 0;
}