UVA 10034 Freckles

 

大意：使用最小连线使得所有给定的点连在一起。

思路：最小生成树。

CODE：

 

#include <iostream>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <cmath>
using namespace std;


#define MAXN 110
#define INF 0X3F3F3F3F

struct node
{
    double x, y;
}a[MAXN];

double w[MAXN][MAXN], d[MAXN];
int n;

double dist(node a, node b)
{
    return sqrt((a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y));
}

double Prim(int src)
{
    bool vis[MAXN] = {0};
    double cnt = 0;
    for(int i = 1; i <= n; i++) d[i] = (i == src)?0:INF;
    for(int i = 1; i <= n; i++)
    {
        int x;
        double m = INF;
        for(int y = 1; y <= n; y++) if(d[y] < m && !vis[y]) m = d[x=y];
        vis[x] = 1;
        cnt += m;
        for(int y = 1; y <= n; y++) d[y] = min(d[y], w[x][y]);
    }
    return cnt;    
}

void init()
{
    memset(w, INF, sizeof(INF));
}

int main()
{
    int T;
    scanf("%d", &T);
    while(T--)
    {
        init();
        scanf("%d", &n);
        for(int i = 1; i <= n; i++)
        {
            scanf("%lf%lf", &a[i].x, &a[i].y);
        }
        for(int i = 1; i <= n; i++)
        {
            for(int j = 1; j <= n; j++)
            {
                if(i == j) continue;
                w[i][j] = dist(a[i], a[j]);
            }
        }
        double ans = Prim(1);
        printf("%.2lf\n", ans);
        if(T) printf("\n");
    }
    return 0;
}