Submission #1072770

#	Time	Username	Problem	Language	Result	Execution time	Memory
1072770		kym	Building Skyscrapers (CEOI19_skyscrapers)	C++14	0 / 100	3586 ms	25332 KiB

skyscrapers

#include <bits/stdc++.h>
using namespace std;
#define int long long 
typedef pair<int,int>pi;
const int oo = 1'000'000'000'000'000'000ll;
int dx[]={0,1,1,1,0,-1,-1,-1};
int dy[]={1,1,0,-1,-1,-1,0,1};
vector<int>ord;
vector<int>cur;
map<pi,int>have;
map<pi,int>idx;
map<pi,int>vis;
map<int,pi>coord;
void dfs(pi cc){
	vis[cc]=1;
	cur.push_back(idx[cc]);
	int x=cc.first,y=cc.second;
	for(int k=0;k<8;k++){
		int nx=x+dx[k];
		int ny=y+dy[k];
		if(have.find({nx,ny}) != have.end() && !vis[{nx,ny}]){
			dfs({nx,ny});
			return; 
		}
	}
}
vector<int>boundary(set<pi> S){//we must exclude the articulation points also 
	vector<pi> X;
	for(auto x:S)X.push_back(x);
	sort(X.begin(),X.end(),[](pi x, pi y){
		if(x.first != y.first)return x.first<y.first;
		else return x.second>y.second;
	});
	have.clear();
	cur.clear();
	for(auto x:X)have[x]=1;
	vis.clear();
	dfs(X[0]);
	//now check if it's a cycle or not
	// it is a cycle iff for the boundary nodes each node has >=2 neighbours
	if(cur.size() != have.size()) return cur; // must be a cyc, so removing any works
	//everyone is on the boundary, so check if line or cyc
	vector<int>ends;
	for(auto zz:cur){
		int cnt=0;
		pi cc=coord[zz];
		int x=cc.first,y=cc.second;
		for(int k=0;k<8;k++){
			int nx=x+dx[k];
			int ny=y+dy[k];
			if(have.find({nx,ny}) != have.end()){
				++cnt;
			}
		}
		assert(cnt!=0);
		if(cnt==1){
			ends.push_back(x);
		}
	}
	if(ends.empty())return cur;
	else return ends;
	
}
set<pi>ss;

pi mn=make_pair(oo,oo);
map<pi,bool>done;
int n,t;
void test(){
	
	priority_queue<pi,vector<pi>,greater<pi>>pq;
	vector<int>ord;
	pq.push(mn);
	done[mn]=1;
	while(pq.size()){
		pi cur=pq.top();pq.pop();
		int x=cur.first,y=cur.second;
		ord.push_back(idx[{x,y}]);
		for(int k=0;k<8;k++){
			int nx=x+dx[k],ny=y+dy[k];
			if(idx.find({nx,ny}) != idx.end() && !done[{nx,ny}]){
				done[{nx,ny}]=1;
				pq.push({nx,ny});
			}
		}
	}
	if(ord.size() != n){
		cout<<"NO\n";exit(0);
	}
	done.clear();
}
int32_t main(){
	cin>>n>>t;
	for(int i=1;i<=n;i++){
		int x,y;cin>>x>>y;
		coord[i]={x,y};
		idx[{x,y}]=i;
		ss.insert({x,y});
		mn=min(mn,make_pair(x,y));
	}
	test();
	while(ord.size()<n){
		vector<int>R=boundary(ss);
		int mx=0;
		for(auto x:R)mx=max(mx,x);
		
		ss.erase(coord[mx]);
		ord.push_back(mx);
	}
	reverse(ord.begin(),ord.end());
	cout<<"YES\n";
	for(auto x:ord)cout<<x<<"\n";
}

Compilation message (stderr)

skyscrapers.cpp: In function 'void test()':
skyscrapers.cpp:87:16: warning: comparison of integer expressions of different signedness: 'std::vector<long long int>::size_type' {aka 'long unsigned int'} and 'long long int' [-Wsign-compare]
   87 |  if(ord.size() != n){
      |     ~~~~~~~~~~~^~~~
skyscrapers.cpp: In function 'int32_t main()':
skyscrapers.cpp:102:18: warning: comparison of integer expressions of different signedness: 'std::vector<long long int>::size_type' {aka 'long unsigned int'} and 'long long int' [-Wsign-compare]
  102 |  while(ord.size()<n){
      |        ~~~~~~~~~~^~

• Subtask 1: 0 / 8
• Subtask 2: 0 / 14
• Subtask 3: 0 / 12
• Subtask 4: 0 / 17
• Subtask 5: 0 / 20
• Subtask 6: 0 / 10
• Subtask 7: 0 / 19