poj2560 kruscal

只看看数据就知道怎么回事了，花5分钟又写了遍kruscal，的确经典！

#include <iostream>#include <algorithm>#include <cmath>using namespace std;struct point { double x,y;}p[110];struct edge { int x,y; double c;}a[10010];int n,tot,i,j,k1,k2,f[110];double ans;int find(int i) { if (i!=f[i]) f[i]=find(f[i]); return f[i];}double dis(point a, point b) { return pow((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y),0.5);}bool cmp(edge a,edge b) { return a.c<b.c;}int main() { tot=0; cin >> n; for (i=1;i<=n;i++) { cin >> p[i].x >> p[i].y; for (j=1;j<i;j++) { tot++; a[tot].x=i; a[tot].y=j; a[tot].c=dis(p[i],p[j]); } } sort(a+1,a+tot+1,cmp); ans=0; for (i=1;i<=n;i++) f[i]=i; for (i=1;i<=tot;i++) { k1=find(a[i].x); k2=find(a[i].y); if (k1!=k2) { f[k1]=k2; ans+=a[i].c; } } printf("%.2lf/n",ans); //system("pause"); return 0;}