Hdu 1162 Eddy's picture

最小生成树。

CODE：

 

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>     //INT_MAX,整形范围内的最大整数。
#include <algorithm>
using namespace std;

#define INF 0x3f3f3f3f
const int SIZE = 110;


double w[SIZE][SIZE];
double d[SIZE];
int v[SIZE];
int n;

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

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



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

void init()
{
    memset(v, 0, sizeof(v));
    memset(d, 0, sizeof(d));
    memset(a, 0, sizeof(a));
    for(int i = 1; i <= SIZE; i++)
        for(int j = 1; j <= SIZE; j++)
            w[i][j] = INF;
}



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