最小生成树（prim）

[c++]代码库

#include<stdio.h>
#include<string.h>
#include<math.h>

const int maxn = 100 + 5;
const int INF = 1e9;
int x[maxn];
int y[maxn];
int vis[maxn];
double low[maxn];
double G[maxn][maxn];

double prim(int n)
{
    double res = 0;
    double min;
    int i,j,pos;
    vis[1] = 1;
    pos = 1;
    for(i = 1; i <= n; i++)
        if(i != pos) low[i]=G[pos][i];
    for(i=1; i<n; i++)
    {
        min=INF;
        for(j=1; j<=n; j++)
        {
            if(vis[j]==0&&min>low[j])
            {
                min=low[j];
                pos=j;
            }
        }
        if(min == INF)
            break;
        res += min;
        vis[pos]=1;
        for(j=1; j<=n; j++)
            if(vis[j]==0 && low[j]>G[pos][j])
                low[j]=G[pos][j];
    }
    if(i != n)
        return -1;
    return res;
}
int main()
{
    int T;
    scanf("%d",&T);
    while(T--)
    {
        memset(G,0,sizeof(G));
        memset(vis,0,sizeof(vis));
        int n,e;
        scanf("%d",&n);
        for(int i = 1; i <= n; i++)
        {
            scanf("%d%d",&x[i],&y[i]);
            for(int j = 1; j < i; j++)
            {
                double t = (x[i]-x[j])*(x[i]-x[j]) + (y[i]-y[j])*(y[i]-y[j]);
                t = sqrt(t);
                if(t >= 10.0 && t <= 1000.0)
                    G[i][j] = G[j][i] = t;
                else
                    G[i][j] = G[j][i] = INF;
            }
        }
        double ans = prim(n);
        ans *= 100;
        if(ans > 0)
            printf("%.1lf\n",ans);
        else
            printf("oh!\n");
    }
    return 0;
}

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