Submission #748884

#	Time	Username	Problem	Language	Result	Execution time	Memory
748884		wenqi	Ancient Books (IOI17_books)	C++17	22 / 100	2068 ms	115436 KiB

books

#include "books.h"
#include <algorithm>
#include <cmath>
#include <cstring>
#include <iostream>
#include <queue>
#include <set>

using namespace std;
using ll = long long;

bool seen[1000005];
vector<int> P;
vector<int> t;

struct Node
{
	int mn, mx;
};

Node nodes[8000005];

void upd(int i, int l, int r, int p, int mn, int mx)
{
	auto &node = nodes[i];
	if (p < l or p > r)
		return;
	if (l == r)
	{
		node.mn = mn;
		node.mx = mx;
		return;
	}
	int m = (l + r) / 2;
	upd(2 * i, l, m, p, mn, mx);
	upd(2 * i + 1, m + 1, r, p, mn, mx);
	node.mn = min(nodes[2 * i].mn, nodes[2 * i + 1].mn);
	node.mx = max(nodes[2 * i].mx, nodes[2 * i + 1].mx);
}

pair<int, int> query(int i, int l, int r, int ql, int qr)
{
	auto &node = nodes[i];
	if (qr < l or ql > r)
		return {1e9, 0};
	if (ql <= l and qr >= r)
		return {node.mn, node.mx};
	int m = (l + r) / 2;
	auto A = query(2 * i, l, m, ql, qr);
	auto B = query(2 * i + 1, m + 1, r, ql, qr);
	return {min(A.first, B.first), max(A.second, B.second)};
}

ll dfs(int i)
{
	if (seen[i])
		return 0;
	seen[i] = true;
	t.push_back(i);
	return abs(i - P[i]) + dfs(P[i]);
}

ll minimum_walk(vector<int> p, int s)
{
	P = p;
	ll sum = 0;
	int n = p.size();
	vector<pair<int, int>> q;
	q.push_back({s, s});
	bool lol = false;
	for (auto &n : nodes)
		n.mn = 1e9;
	for (int i = 0; i < n; i++)
	{
		if (seen[i] or i == p[i])
			continue;
		t.clear();
		sum += dfs(i);
		sort(t.begin(), t.end());
		q.push_back({t.front(), t.back()});
		auto [a, b] = q.back();
		for (int x : t)
			upd(1, 0, n, x, a, b);
		// if (a <= s and s <= b)
		// 	lol = true;
	}
	sort(q.begin(), q.end());
	int st = 0;
	int lt = -1;
	int pl, pr;
	for (auto [a, b] : q)
	{
		if (lt == -1)
		{
			st = a;
			lt = b;
		}
		if (a > lt)
		{
			if (st <= s and s <= lt)
			{
				lol = true;
				pl = st, pr = lt;
			}
			sum += 2 * (a - lt);
			lt = b;
			st = a;
		}
		else
		{
			lt = max(lt, b);
		}
	}
	if (st <= s and s <= lt)
	{
		lol = true;
		pl = st, pr = lt;
	}
	if (pl == pr)
		lol = false;
	for (int p = 0; p < 21; p++)
	{
		for (int i = 0; i < n; i++)
		{
			auto [a, b] = query(1, 0, n, i, i);
			auto [x, y] = query(1, 0, n, a, b);
			// printf("%d %d %d\n", i, x, y);
			upd(1, 0, n, i, x, y);
		}
	}
	int mn = 1e9;
	for (int i = 0; i < n; i++)
	{
		auto [a, b] = query(1, 0, n, i, i);
		if (a <= pl and pr <= b)
			mn = min(mn, abs(i - s));
	}
#ifdef DEBUG
	printf("%d %d\n", lol, mn);
#endif
	if (lol)
		sum += 2 * mn;
	return sum;
}

Compilation message (stderr)

books.cpp: In function 'll minimum_walk(std::vector<int>, int)':
books.cpp:119:2: warning: 'pr' may be used uninitialized in this function [-Wmaybe-uninitialized]
  119 |  if (pl == pr)
      |  ^~
books.cpp:119:2: warning: 'pl' may be used uninitialized in this function [-Wmaybe-uninitialized]

• Subtask 1: 12 / 12
• Subtask 2: 10 / 10
• Subtask 3: 0 / 28
• Subtask 4: 0 / 20
• Subtask 5: 0 / 30