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;
}