题目链接
思路:每次贪心的选择度最大的点进入生成树
#include<bits/stdc++.h>
using namespace std;
const int maxn=2e5+5;
int du[maxn],father[maxn],num[maxn];
vector<pair<int,int>>ans;
vector<int>g[maxn];
int findfather(int x)
{
if(x==father[x]) return x;
int i=findfather(father[x]);
father[x]=i;
return i;
}
bool cmp(const int a,const int b)
{
return du[a]>du[b];
}
int main()
{
int n,m,u,v;
scanf("%d %d",&n,&m);
for(int i=0;i<=n;++i) num[i]=i,father[i]=i;
for(int i=1;i<=m;++i)
{
scanf("%d %d",&u,&v);
g[u].push_back(v);
g[v].push_back(u);
du[u]++,du[v]++;
}
sort(num+1,num+1+n,cmp);
int cnt=0;
for(int i=1;i<=n&&cnt!=n-1;++i)
{
for(int j:g[num[i]])
{
int fa=findfather(num[i]),fb=findfather(j);
if(fa!=fb) cnt++,ans.push_back({num[i],j}),father[fa]=fb;
}
}
for(auto i:ans) printf("%d %d\n",i.first,i.second);
}