Submission #793860

#	Time	Username	Problem	Language	Result	Execution time	Memory
793860		ymm	IOI Fever (JOI21_fever)	C++17	6 / 100	1 ms	812 KiB

fever

#include <bits/stdc++.h>
#define Loop(x,l,r) for (ll x = (l); x < (r); ++x)
typedef long long ll;
typedef std::pair<int,int> pii;
using namespace std;

const int N = 100'010;
map<int,vector<int>> wa, as, sd, dw;
int X[N], Y[N];
int dis[N];
int n;

enum dir { W, A, S, D};
map<int,vector<int>> *dvec[4][2] = {
	{&dw, &wa},
	{&as, &wa},
	{&as, &sd},
	{&dw, &sd},
};

pair<int,dir> colide(int i, int j, dir d)
{
	int x = X[j] - X[i];
	int y = Y[j] - Y[i];
	assert(abs(x) == abs(y));
	switch (d) {
		case W: return {y, x > 0? A: D};
		case A: return {-x, y > 0? S: W};
		case S: return {-y, x > 0? A: D};
		case D: return {x, y > 0? S: W};
	}
}

int bfs(int v, dir d)
{
	vector<pair<int,dir>> q = {{v, d}};
	memset(dis, -1, sizeof(dis));
	dis[v] = 0;
	Loop (i,0,q.size()) {
		auto [v, d] = q[i];
		auto &vec1 = (*dvec[d][0])[X[v]-Y[v]];
		auto &vec2 = (*dvec[d][1])[X[v]+Y[v]];
		for (auto _vec : {&vec1, &vec2}) {
			auto &vec = *_vec;
			while (vec.size()) {
				int u = vec.back();
				if (dis[u] != -1) {
					vec.pop_back();
					continue;
				}
				auto [di, d2] = colide(v, u, d);
				if (di < dis[v])
					break;
				vec.pop_back();
				dis[u] = di;
				q.push_back({u, d2});
			}
		}
	}
	return q.size();
}

int main()
{
	cin.tie(0) -> sync_with_stdio(false);
	cin >> n;
	Loop (i,0,n)
		cin >> X[i] >> Y[i];
	int ans = 0;
	for (auto d : {W, A, S, D}) {
		for (auto mp : {&dw, &wa, &as, &sd})
			for (auto &[_, vec] : *mp)
				vec.clear();
		Loop (i,0,n) {
			dw[X[i]-Y[i]].push_back(i);
			wa[X[i]+Y[i]].push_back(i);
			as[X[i]-Y[i]].push_back(i);
			sd[X[i]+Y[i]].push_back(i);
		}
		for (auto &[_, vec] : dw) sort(vec.begin(), vec.end(), [&](int i, int j){ return X[i] < X[j]; });
		for (auto &[_, vec] : wa) sort(vec.begin(), vec.end(), [&](int i, int j){ return X[i] > X[j]; });
		for (auto &[_, vec] : as) sort(vec.begin(), vec.end(), [&](int i, int j){ return X[i] > X[j]; });
		for (auto &[_, vec] : sd) sort(vec.begin(), vec.end(), [&](int i, int j){ return X[i] < X[j]; });
		ans = max(ans, bfs(0, d));
	}
	cout << ans << '\n';
}

Compilation message (stderr)

fever.cpp: In function 'int bfs(int, dir)':
fever.cpp:2:40: warning: comparison of integer expressions of different signedness: 'll' {aka 'long long int'} and 'std::vector<std::pair<int, dir> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    2 | #define Loop(x,l,r) for (ll x = (l); x < (r); ++x)
      |                                        ^
fever.cpp:39:2: note: in expansion of macro 'Loop'
   39 |  Loop (i,0,q.size()) {
      |  ^~~~
fever.cpp: In function 'std::pair<int, dir> colide(int, int, dir)':
fever.cpp:32:1: warning: control reaches end of non-void function [-Wreturn-type]
   32 | }
      | ^

• Subtask 1: 0 / 5
• Subtask 2: 0 / 8
• Subtask 3: 6 / 6
• Subtask 4: 0 / 6
• Subtask 5: 0 / 12
• Subtask 6: 0 / 32
• Subtask 7: 0 / 31