NC15108 道路建设

\(MST\)裸题

const int N=110;
int g[N][N];
int dist[N];
bool vis[N];
int money;
int n,m;

int prim()
{
    memset(dist,0x3f,sizeof dist);
    memset(vis,0,sizeof vis);
    dist[1]=0;
    int res=0;

    for(int i=0;i<n;i++)
    {
        int t=-1;
        for(int j=1;j<=n;j++)
            if(!vis[j] && (t==-1 || dist[t]>dist[j]))
                t=j;
        if(dist[t] == INF) return -1;

        vis[t]=true;
        res+=dist[t];

        for(int j=1;j<=n;j++)
            dist[j]=min(dist[j],g[t][j]);
    }
    return res;
}

int main()
{
    while(cin>>money>>m>>n)
    {
        memset(g,0x3f,sizeof g);

        while(m--)
        {
            int a,b,c;
            cin>>a>>b>>c;
            g[a][b]=min(g[a][b],c);
        }

        int t=prim();
        if(~t && t<=money) puts("Yes");
        else puts("No");
    }

    //system("pause");
}