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  • HDU1863畅通工程---并查集+最小生成树

    #include<cstdio>
    #include<algorithm>
    #define MAX 105
    
    struct edge
    {
        int from,to;
        long long cost;
    }lm[MAX*MAX];
    
    int N,M,father[MAX],i;
    
    bool cmp(edge a,edge b)
    {
        return a.cost<b.cost;
    }
    
    void init()
    {
        for(int i=1;i<=N;i++)
            father[i]=i;
    }
    
    int Find(int x)
    {
        if(x==father[x])return x;
        return father[x]=Find(father[x]);
    }
    
    bool Same(int x,int y)
    {
        return Find(x)==Find(y);
    }
    
    void unionset(int x,int y)
    {
        int u=Find(x),v=Find(y);
        if(u==v)return;
        father[u]=v;
    }
    
    long long kruskal()
    {
        long long res=0;
        std::sort(lm+1,lm+1+M,cmp);
        for(i=1;i<=M;i++)
        {
            if(Same(lm[i].from,lm[i].to))continue;
            unionset(lm[i].from,lm[i].to);
            res+=lm[i].cost;
        }
        return res;
    }
    
    int main()
    {
        while(scanf("%d%d",&M,&N)==2)
        {
            if(!M)break;
            init();
            for(i=1;i<=M;i++)
            {
                scanf("%d%d%lld",&lm[i].from,&lm[i].to,&lm[i].cost);
            }
            long long res=kruskal();
            for(i=1;i<=N;i++)
                if(!Same(i,1))
                    res=-1;
            if(res==-1)
                printf("?
    ");
            else
                printf("%lld
    ",res);
        }
        return 0;
    }
    

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  • 原文地址:https://www.cnblogs.com/gfvod/p/5548310.html
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