hdu 1162 Eddy's picture(最小生成树Kruskal)

/*
Author: ACb0y
Date: 2010年9月16日1:06:03
Type: MST Kruskal
ProblemId: hdu 1162 Eddy's picture
Result: 2960095 2010-09-16 01:04:47 Accepted 1162 15MS 480K 1267 B G++ ACb0y
*/
#include <iostream>
#include <cmath>
using namespace std;

struct Point {
double x;
double y;
};

struct edge {
int x;
int y;
double w;
};

int n;
int g[110][110];
int father[110];
Point points[110];
edge edges[10100];

double get_dis(int a, int b) {
return sqrt((points[a].x - points[b].x) * (points[a].x - points[b].x) +
(points[a].y - points[b].y) * (points[a].y - points[b].y));
}

int cmp(const void * a, const void * b) {
edge * pa = (edge *) a;
edge * pb = (edge *) b;
return pa->w > pb->w ? 1 : -1;
}

int find(int x) {
if (x != father[x]) {
return find(father[x]);
}
return x;
}

int main()
{
int i, j;
#ifndef ONLINE_JUDGE
freopen("1162.txt", "r", stdin);
#endif
while (cin >> n) {
for (i = 1; i <= n; i++) {
scanf("%lf%lf", &points[i].x, &points[i].y);
}
int c = 0;
for (i = 1; i <= n; i++) {
for (j = 1; j <= n; j++) {
edges[c].w = get_dis(i, j);
edges[c].x = i;
edges[c].y = j;
c++;
}
}
qsort(edges, c, sizeof(edge), cmp);
for (i = 1; i <= n; i++) {
father[i] = i;
}
double ans = 0;
for (i = 0; i < c; i++) {
int x = find(edges[i].x);
int y = find(edges[i].y);
if (x != y) {
ans += edges[i].w;
father[x] = y;
}
}
printf("%.2lf/n", ans);
}
return 0;
}