Codeforces Round #762 (Div. 3) G. Unusual Minesweeper

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=2e5+10;
int t,n,k,fa[N],val[N];
struct node{int a,b,c,d;}p[N];
map< int, vector<pair<int,int>> > v,v2;
void init(){for(int i=1;i<=n;i++) fa[i]=i,val[i]=p[i].c;}
int find(int x){
    if(fa[x]==x) return x;
    else return fa[x]=find(fa[x]);
}
void Union(int x,int y){
    int fx=find(x),fy=find(y);
    if(fx==fy) return ;
    val[fy]=min(val[fy],val[fx]);
    fa[fx]=fy;
}
bool check(vector<int> v,int x){
    int index=upper_bound(v.begin(),v.end(),x)-v.begin();
    int nd=v.size()-index;
    return x+1>=nd;
}
int main(){
    scanf("%d",&t);
    while(t--){
        scanf("%d%d",&n,&k);
        v.clear();v2.clear();
        for(int i=1;i<=n;i++){
            int x,y,tim;scanf("%d%d%d",&x,&y,&tim);
            p[i]={x,y,tim,i};v[x].push_back({y,i});v2[y].push_back({x,i});
        }
        init();
        for(auto now:v){
            sort(now.second.begin(),now.second.end());
            for(int i=1;i<now.second.size();i++){
                if(now.second[i].first-now.second[i-1].first<=k){
                    Union(now.second[i].second,now.second[i-1].second);
                }
            }
        }
        for(auto now:v2){
            sort(now.second.begin(),now.second.end());
            for(int i=1;i<now.second.size();i++){
                if(now.second[i].first-now.second[i-1].first<=k){
                    Union(now.second[i].second,now.second[i-1].second);
                }
            }
        }
        // int cnt=0;for(int i=1;i<=n;i++) if(fa[i]==i) ++cnt;cout<<cnt<<endl;
        vector<int> eva;
        for(int i=1;i<=n;i++) if(fa[i]==i) eva.push_back(val[i]);
        sort(eva.begin(),eva.end());
        // for(auto it:eva) cout<<it<<" ";cout<<endl;
        int l=0,r=1e9;
        while(l<r){
            int mid=(l+r)>>1;
            if(check(eva,mid)) r=mid;
            else l=mid+1;
        }
        cout<<l<<endl;
    }
}