Submission #503982

#	Time	Username	Problem	Language	Result	Execution time	Memory
503982		sidon	Road Construction (JOI21_road_construction)	C++17	100 / 100	4915 ms	48708 KiB

road_construction

#include <bits/stdc++.h>
using namespace std;
 
#define C(Z) lower_bound(xVals, xVals + N, Z) - xVals
#define int int64_t
 
int N, K, F[250'001];
 
void add(int i, int v) {
	for(i++; i <= N; i += i&-i) F[i] += v;
}
 
int get(int i, int v = 0) {
	for(i++; i >= 1; i -= i&-i) v += F[i];
	return v;
}
 
int32_t main() {
	ios::sync_with_stdio(0), cin.tie(0);
 
	cin >> N >> K;
 
	int X[N], Y[N], byY[N], xVals[N], xPos[N];
 
	for(int i = 0, x, y; i < N; ++i) {
		cin >> x >> y;
		X[i] = x + y;
		Y[i] = x - y;
		byY[i] = i;
		xVals[i] = X[i];
	}
 
	sort(byY, byY + N, [&](int &i, int &j) {
		return Y[i] < Y[j];
	});
	sort(xVals, xVals + N);
 
	for(int i = 0; i < N; ++i)
		xPos[i] = C(X[i]);
 
	int dist = -1, ext;
 
	for(int b = 1LL<<33; b /= 2; ) {
		dist += b;
 
		int f = 0;
		int p = 0;
		fill(F, F + N + 1, 0);
 
		for(int i : byY) {
			while(Y[i] - Y[byY[p]] > dist)
				add(xPos[byY[p++]], -1);
 
			f += get(C(X[i] + dist + 1)-1);
			f -= get(C(X[i] - dist + 0)-1);
 
			add(xPos[i], 1);
		}
 
		if(f >= K) dist -= b;
		else ext = K - f;
	}
	++dist;
 
	set<array<int, 2>> on;
	priority_queue<int> ans;
	map<int, int> done[N];
 
	int p = 0;
 
	for(int i : byY) {
		while(Y[i] - Y[byY[p]] > dist)
			on.erase({X[byY[p]], byY[p]}), ++p;
 
		auto j = on.lower_bound({(X[i] - dist), -1});
		bool nxt = 1;
 
		while(j != end(on) && (*j)[0] <= X[i] + dist) {
			int o = (*j)[1];
			int r = max(abs(X[i] - X[o]), Y[i] - Y[o]);
			if(r == dist && !--ext) {
				--dist;
 
				while(Y[i] - Y[byY[p]] > dist)
					on.erase({X[byY[p]], byY[p]}), ++p;
 
				j = on.lower_bound({(X[i] - dist), -1});
				nxt = 0;
			}
			if(++done[o][i] < 2) ans.push(-r);
			if(nxt) ++j;
			nxt = 1;
		}
 
		on.insert({X[i], i});
	}
 
	while(!empty(ans))
		cout << -ans.top() << '\n', ans.pop();
}

Compilation message (stderr)

road_construction.cpp: In function 'int32_t main()':
road_construction.cpp:81:17: warning: 'ext' may be used uninitialized in this function [-Wmaybe-uninitialized]
   81 |    if(r == dist && !--ext) {
      |       ~~~~~~~~~~^~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 6 / 6
• Subtask 3: 7 / 7
• Subtask 4: 20 / 20
• Subtask 5: 27 / 27
• Subtask 6: 35 / 35