传送门:https://www.luogu.org/problemnew/show/P2330
终于做对了一个图论+二分的题,虽然比较简单吧,是个黄题...
直接prim求一下最小生成树,然后就二分一下分值就好啦!
#include <bits/stdc++.h>
using namespace std;
const int maxn = 330;
const int INF = 1e9+7;
int vis[maxn];
int n,m;
int cnt = 0;
struct node
{
int to;
int cost;
bool operator<(const node &a)const
{
return cost>a.cost;
}
};
vector<node> G[maxn];
int prim(int s,int x)
{
int ans = 0;
priority_queue<node> q;
vis[s] = 1;
for(int i=0;i<G[s].size();i++)
{
q.push(G[s][i]);
}
while(!q.empty())
{
node tmp = q.top();
q.pop();
if(vis[tmp.to]) continue;
if(tmp.cost<=x)
{
cnt++;
vis[tmp.to] = 1;
ans += tmp.cost;
for(int i=0;i<G[tmp.to].size();i++)
{
q.push(G[tmp.to][i]);
}
}
}
return ans;
}
bool check(int x)
{
memset(vis,0,sizeof(vis));
cnt = 0;
prim(1,x);
for(int i=1;i<=n;i++)
{
if(!vis[i])
{
return false;
}
}
return true;
}
int main()
{
ios::sync_with_stdio(false);
cin.tie(0);
cin>>n>>m;
int l = INF,r = 0;
for(int i=0;i<m;i++)
{
int x,y,z;
cin>>x>>y>>z;
G[x].push_back((node){y,z});
G[y].push_back((node){x,z});
l = min(l,z);
r = max(r,z);
}
int ans = 0;
int res = 0;
while(l<=r)
{
int mid = (l+r)/2;
if(check(mid))
{
res = cnt;
ans = mid;
r = mid-1;
}
else
{
l = mid+1;
}
}
cout<<res<<" "<<ans<<endl;
return 0;
}