Submission #252832

#	Time	Username	Problem	Language	Result	Execution time	Memory
252832		user202729	Circle selection (APIO18_circle_selection)	C++17	49 / 100	3083 ms	50132 KiB

circle_selection

// C++'s implicit behavior is usually comfortable and sometimes annoying.
#ifndef LOCAL
#define NDEBUG 1
#endif
#include<bits/stdc++.h>

int main(){
	std::ios::sync_with_stdio(0);std::cin.tie(0);

	using Index=int; // for circles
	struct Circle{
		int x, y, r;
		bool intersect(Circle other) const{
			assert(r>0); assert(other.r>0);
			return int64_t(x-other.x)*(x-other.x)+int64_t(y-other.y)*(y-other.y)<=
				int64_t(r+other.r)*(r+other.r);
		}
	};
	int number; std::cin>>number;
	std::vector<Circle> circles(number);
	for(auto& [x, y, r]: circles)
		std::cin>>x>>y>>r; // r==0: deleted

	struct A{
		Index index; int r;
		bool operator<(A other) const{
			return r!=other.r ? r<other.r: index>other.index;
		}
	};
	std::priority_queue<A> q;
	for(Index index=0; index<number; ++index)
		q.push({index, circles[index].r});

	auto const callIf=[&](auto& object, int key, auto function){
		auto const iterator=object.find(key);
		if(iterator!=object.end()) function(iterator->second);
	};

	std::vector<int> result(number);
	assert((result.assign(number, -1), true));

	std::map<int, std::map<int, std::vector<Index>>> grid;
	for(int step=30; step;--step){
		grid.clear();
		for(Index index=0; index<number; ++index){
			auto const [x, y, r]=circles[index];
			if(r==0) continue;
			assert(r<(1<<step));
		
			grid[x>>step][y>>step].push_back(index);
		}

		while(true){
			if(q.empty())
				goto break_outer;

			auto [index, r_]=q.top();
			auto const cur=circles[index]; auto const [x, y, r]=cur;
			if(r==0) {
				q.pop();
				continue;
			}
			assert(r==r_);
			if(r<((1<<step)>>1))
				break; // goto next step -- without popping from q

			q.pop();
			circles[index].r=0;

			assert(result[index]==-1); result[index]=index;
			for(int a=-2; a<=2;++a)
				callIf(grid, (x>>step)+a, [&](auto& it){
					for(int b=-2; b<=2; ++b)
						callIf(it, (y>>step)+b, [&](auto& it){
							it.erase(std::remove_if(begin(it), end(it), [&](Index index1){
								if(a==0 and b==0){
									if(index1==index){
										return true;
									}
								}else assert(index1!=index);

								auto& cur1=circles[index1];
								assert(cur1.r>0);
								if(cur1.intersect(cur)){
									assert(result[index1]==-1);
									result[index1]=index;
									cur1.r=0;
									return true;
								} else return false;
							}),it.end());
							assert(std::cerr<<"");
						});
				});
		}
	}
break_outer:

	for(Index index=0; index<number; ++index){
		auto const [x, y, r]=circles[index];
		assert(result[index]!=-1);
		assert(r==0);
	}

	for(auto it: result) std::cout<<it+1<<' ';
	std::cout<<'\n';
}

Compilation message (stderr)

circle_selection.cpp: In function 'int main()':
circle_selection.cpp:57:19: warning: unused variable 'r_' [-Wunused-variable]
    auto [index, r_]=q.top();
                   ^
circle_selection.cpp:99:22: warning: unused variable 'x' [-Wunused-variable]
   auto const [x, y, r]=circles[index];
                      ^
circle_selection.cpp:99:22: warning: unused variable 'y' [-Wunused-variable]
circle_selection.cpp:99:22: warning: unused variable 'r' [-Wunused-variable]

• Subtask 1: 7 / 7
• Subtask 2: 12 / 12
• Subtask 3: 0 / 15
• Subtask 4: 0 / 23
• Subtask 5: 30 / 30
• Subtask 6: 0 / 13