Submission #1302831

#TimeUsernameProblemLanguageResultExecution timeMemory
1302831vache_kocharyanObstacles for a Llama (IOI25_obstacles)C++20
23 / 100
2100 ms146896 KiB
#include "obstacles.h"
#include <bits/stdc++.h>
#include <unordered_map>
#include <chrono>

#define TIME_LIMIT_SECONDS 0.5

using namespace std;
using namespace chrono;

struct hash_pair {
	size_t operator()(const pair<int, int>& p) const {
		return ((size_t)p.first << 32) ^ (size_t)p.second;
	}
};

unordered_map<pair<int, int>, int, hash_pair> ump;

const int N = 4e5 + 10;
const int M = 2e5 + 10;
const int LOG = 21;

vector<int>T, H;
int n, m;

int log2_(int x)
{
	return 31 - __builtin_clz(x);
	//return int(log2(x));
}

struct sparse_table
{
	vector<int>a;
	int sp_mx[M][LOG];
	int sp_mn[M][LOG];
	int id_mn[M][LOG];
	int id_mx[M][LOG];

	void build_sparse(vector<int>H)
	{
		int m_ = H.size();
		a = H;
		for (int i = 0; i < m_; i++)
		{
			sp_mn[i][0] = H[i];
			sp_mx[i][0] = H[i];
			id_mn[i][0] = i;
			id_mx[i][0] = i;
		}

		for (int j = 1; j < LOG; j++)
		{
			for (int i = 0; i + (1 << j) <= m_; i++)
			{
				int mid = i + (1 << (j - 1));

				if (sp_mx[i][j - 1] >= sp_mx[mid][j - 1]) {
					sp_mx[i][j] = sp_mx[i][j - 1];
					id_mx[i][j] = id_mx[i][j - 1];
				}
				else {
					sp_mx[i][j] = sp_mx[mid][j - 1];
					id_mx[i][j] = id_mx[mid][j - 1];
				}

				if (sp_mn[i][j - 1] <= sp_mn[mid][j - 1]) {
					sp_mn[i][j] = sp_mn[i][j - 1];
					id_mn[i][j] = id_mn[i][j - 1];
				}
				else {
					sp_mn[i][j] = sp_mn[mid][j - 1];
					id_mn[i][j] = id_mn[mid][j - 1];
				}
			}
		}
	}

	int query_mx(int l, int r)
	{
		int lg = log2_(r - l + 1);
		return max(sp_mx[l][lg], sp_mx[r - (1 << lg) + 1][lg]);
	}

	int query_mn(int l, int r)
	{
		int lg = log2_(r - l + 1);
		return min(sp_mn[l][lg], sp_mn[r - (1 << lg) + 1][lg]);
	}

	int query_id_mx(int l, int r)
	{
		int lg = log2_(r - l + 1);
		int a = sp_mx[l][lg], b = sp_mx[r - (1 << lg) + 1][lg];
		if (a >= b) return id_mx[l][lg];
		return id_mx[r - (1 << lg) + 1][lg];
	}

	int query_id_mn(int l, int r)
	{
		int lg = log2_(r - l + 1);
		int a = sp_mn[l][lg], b = sp_mn[r - (1 << lg) + 1][lg];
		if (a <= b) return id_mn[l][lg];
		return id_mn[r - (1 << lg) + 1][lg];
	}

}c_sp, r_sp;

bool is_free(int i, int j)
{
	return T[i] > H[j];
}

int l[N], r[N], right_most_x[N], left_most_x[N], t[N], mn_ind[N];

pair<int, int>find_lr(int ind, int S)
{
	int ansl = S, ansr = S;

	int L = 0, R = S;
	while (L <= R && L >= 0 && R < m)
	{
		int mid = (L + R) / 2;

		if (r_sp.query_mx(mid, S) < T[ind])
		{
			ansl = mid;
			R = mid - 1;
		}
		else
		{
			L = mid + 1;
		}
	}
	L = S, R = m - 1;
	while (L <= R && L >= 0 && R < m)
	{
		int mid = (L + R) / 2;

		if (r_sp.query_mx(S, mid) < T[ind])
		{
			ansr = mid;
			L = mid + 1;
		}
		else
		{
			R = mid - 1;
		}
	}
	return { ansl, ansr };
}

int nxt[N];
int in[N];

int idd[N];

struct dsu_
{
	int p[N], sz[N];
	int n;
	void init(int _n)
	{
		n = _n;
		for (int i = 1; i <= n; i++)
			p[i] = i, sz[i] = 1;
	}

	int find(int a)
	{
		if (a != p[a])
			return p[a] = find(p[a]);
		return p[a];
	}

	void merge(int a, int b)
	{
		a = find(a), b = find(b);
		if (a == b)return;
		if (sz[a] < sz[b])swap(a, b);
		sz[a] += sz[b];
		sz[b] = 0;
		p[b] = a;
	}

	bool ask(int a, int b)
	{
		a = find(a);
		b = find(b);
		return (a == b);
	}
}dsu;

void initialize(std::vector<int> T, std::vector<int> H)
{
	
	n = T.size();
	m = H.size();
	c_sp.build_sparse(T);
	r_sp.build_sparse(H);

	::T = T;
	::H = H;

	int cnt = 0;
	queue<int> cur;

	for (int i = 0; i < m;)
	{
		if (is_free(0, i))
		{
			cnt++;
			cur.push(cnt);
			pair<int, int> P = find_lr(0, i);
			l[cnt] = P.first;
			r[cnt] = P.second;
			i = r[cnt] + 1;
			t[cnt] = 0;
			in[cnt] = r_sp.query_id_mn(l[cnt], r[cnt]);
			ump[{t[cnt], in[cnt]}] = cnt;
			idd[in[cnt]] = cnt;
		}
		else i++;
		assert(cnt <= N);
	}

	while (!cur.empty()) 
	{
		assert(cnt <= N);
		int i = cur.front();
		cur.pop();
		int ind = in[i];
		int cur_mn = T[t[i]];
		int x = t[i] + 1;
		while (x < n)
		{
			cur_mn = min(cur_mn, T[x]);
			if (cur_mn <= H[ind])
				break;
			pair<int, int> P = find_lr(x, ind);
			if (P.first <= l[i] && P.second >= r[i])
			{
				if (P.first < l[i] || P.second > r[i])
				{
					pair<int, int> key = { x, r_sp.query_id_mn(P.first, P.second) };
					if (ump.count(key)) {
						nxt[i] = ump[key];
					}
					else {
						cnt++;
						l[cnt] = P.first;
						r[cnt] = P.second;
						t[cnt] = x;
						ump[key] = cnt;
						cur.push(cnt);
						nxt[i] = cnt;
						in[cnt] = key.second;
					}
					break;
				}
			}
			assert(cnt <= N);
			x++;
		}
	}

	dsu.init(cnt + 10);

	for (int i = 1; i < cnt; i++)
		if (nxt[i])
			dsu.merge(i, nxt[i]);
	assert(cnt <= N);
}

bool can_reach(int L, int R, int S, int D)
{
	if (S > D) swap(S, D);

	if (L != 0 || R != m - 1)
	{
		return false;
	}

	pair<int, int>p1 = find_lr(0, S);
	pair<int, int>p2 = find_lr(0, D);

	int cnt1 = idd[r_sp.query_id_mn(p1.first, p1.second)];
	int cnt2 = idd[r_sp.query_id_mn(p2.first, p2.second)];

	return dsu.ask(cnt1, cnt2);
}
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