Submission #837376

#	Time	Username	Problem	Language	Result	Execution time	Memory
837376		ymm	Thousands Islands (IOI22_islands)	C++17	24 / 100	28 ms	7124 KiB

islands

#include "islands.h"
#include <bits/stdc++.h>
#define Loop(x,l,r) for (ll x = (l); x < ll(r); ++x)
#define LoopR(x,l,r) for (ll x = (r)-1; x >= ll(l); --x)
typedef long long ll;
typedef std::pair<int,int> pii;
using namespace std;

const int N = 100'010;
vector<pii> A[N];
bool vis[N];
bool anc[N];
int height[N];

vector<int> ans;

void answer(int v, int u, int e)
{
	ans.push_back(e);
	int cnt = height[u] - height[v] + 1;
	int pre = ans.size() - cnt;
	Loop (i,pre,pre+cnt)
		ans.push_back(ans[i]^1);
	LoopR (i,pre,pre+cnt)
		ans.push_back(ans[i]^0);
	LoopR (i,pre,pre+cnt)
		ans.push_back(ans[i]^1);
	LoopR (i,0,pre)
		ans.push_back(ans[i]);
}

bool dfs(int v, int h)
{
	height[v] = h;
	vis[v] = 1;
	anc[v] = 1;
	for (auto [u, e] : A[v]) {
		if (anc[u]) {
			answer(u, v, e);
			return 1;
		}
		if (vis[u])
			continue;
		ans.push_back(e);
		if (dfs(u, h+1))
			return 1;
		ans.pop_back();
	}
	anc[v] = 0;
	return 0;
}

std::variant<bool, std::vector<int>> find_journey(
    int N, int M, std::vector<int> U, std::vector<int> V) {
	for (int i = 0; i < M; i += 2)
		A[U[i]].push_back({V[i], i});
	if (!dfs(0, 0))
		return false;
	return ans;
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 5
• Subtask 3: 0 / 21
• Subtask 4: 24 / 24
• Subtask 5: 0 / 45