POJ 1861 Network

来源：互联网发布：js 数组查找编辑：程序博客网时间：2024/04/19 13:00

最小生成树是满足条件的一种树，并不是唯一解

调用qsort后数组从零开始计数。。。被这个搞死了

#include<stdio.h>#include<stdlib.h>#include <cmath>#include <iostream>#include <cstdlib>using namespace std;int parent[15001];int k;struct edge{ int u,v,w;} edges[15001];int compare(const void *a, const void *b){return (*(edge *)a).w - (*(edge *)b).w;}int findset(int x){ int tmp,s; s=x; while (parent[s]>=0) s=parent[s]; while (s!=x) {   tmp=parent[x];   parent[x]=s;   x=tmp; } return s;}void unionset(int r1,int r2){   int rr1,rr2;   rr1=findset(r1);   rr2=findset(r2);   int tmp=parent[rr1]+parent[rr2];   if (rr1==rr2) return;   if (parent[rr1]>parent[rr2]) {                  parent[rr1]=rr2;                  parent[rr2]=tmp;                 }             else {                    parent[rr2]=rr1;                    parent[rr1]=tmp;                  }}int main(){ int a,b,c,n,m,t,ans; edge s[10001]; scanf("%d%d",&n,&m); for (int i=0;i<=n;i++) parent[i]=-1; for (int i=0;i<m;i++) {  scanf("%d%d%d",&a,&b,&c);  edges[i].u=a;  edges[i].v=b;  edges[i].w=c; } qsort(edges,m,sizeof(edges[0]),compare);   ans=0; for (int i=0;i<m;i++) {  if (findset(edges[i].u)!=findset(edges[i].v))                                   {                                     ans=ans+1;                                     s[ans].u=edges[i].u;                                     s[ans].v=edges[i].v;                                     if (ans==(n-1)) t=edges[i].w;                                     unionset(edges[i].u,edges[i].v);                                   }  if (ans>=n-1) break; } printf("%d\n",t); printf("%d\n",ans); for(int i=1;i<=ans;i++) printf("%d %d\n",s[i].u,s[i].v);}