Submission #838310

#	Time	Username	Problem	Language	Result	Execution time	Memory
838310		Johann	Ancient Books (IOI17_books)	C++14	50 / 100	257 ms	58196 KiB

books

#include "books.h"
#include "bits/stdc++.h"
using namespace std;

typedef long long ll;
typedef vector<ll> vi;
typedef vector<vi> vvi;
typedef pair<ll, ll> pii;
typedef vector<pii> vpii;
typedef vector<vpii> vvpii;
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()

const ll INF = 1LL << 60;
int N;
ll safecost;
vi vis, P;

struct unionfind
{
	vi arr;
	vpii stuff;
	void init(int size)
	{
		arr.resize(size);
		stuff.resize(size);
		for (int i = 0; i < size; ++i)
			arr[i] = i, stuff[i] = {i, i};
	}
	int find(int i) { return arr[i] = (arr[i] == i) ? i : find(arr[i]); }
	void unite(int a, int b)
	{
		a = find(a), b = find(b);
		stuff[a] = {min(stuff[a].first, stuff[b].first), max(stuff[a].second, stuff[b].second)};
		arr[b] = a;
	}
	pii border(int i) { return stuff[find(i)]; }
};
unionfind uf;

void cycle(int i, int &mini, int &maxi, int cycleCnt)
{
	if (vis[i] != -1)
		return;
	mini = min(mini, i);
	maxi = max(maxi, i);
	vis[i] = cycleCnt;
	safecost += (ll)abs(P[i] - i);
	uf.unite(i, P[i]);
	cycle(P[i], mini, maxi, cycleCnt);
}

vvpii adj;

long long minimum_walk(std::vector<int> p, int s)
{
	N = sz(p);
	P.resize(N);
	for (int i = 0; i < N; ++i)
		P[i] = p[i];
	uf.init(N);

	vis.assign(N, -1);
	ll L = INF, R = -1;
	safecost = 0;
	vpii borders;
	for (int i = 0, mini, maxi; i < N; ++i)
	{
		if (P[i] != i)
			L = min(L, (ll)i), R = max(R, (ll)i);
		if (vis[i] == -1 && P[i] != i)
		{
			mini = maxi = i;
			cycle(i, mini, maxi, sz(borders));
			borders.push_back({mini, maxi});
		}
	}
	if (borders.empty())
		return 0;
	if (s <= L || s >= R)
	{
		if (s >= R)
		{
			s = N - s;
			for (int i = 0, l, r; i < sz(borders); ++i)
			{
				tie(l, r) = borders[i];
				borders[i] = {N - r, N - l};
			}
		}
		sort(all(borders));

		ll pos = s;
		for (pii b : borders)
		{
			safecost += 2 * max(0LL, b.first - pos);
			pos = max(pos, b.second);
		}

		return safecost;
	}

	stack<int> st;
	for (int i = R; i >= L; --i)
	{
		while (!st.empty() && st.top() <= uf.border(i).second)
		{
			int b = st.top();
			if (b != uf.border(b).first)
				uf.unite(i, b);
			st.pop();
		}
		st.push(i);
	}

	ll l = s, r = s;
	ll nl = l, nr = r;
	do
	{
		if (nl >= 0 && (uf.border(nl).first < l || uf.border(nl).second > r))
		{
			safecost += 2 * (l - nl);
			nl = l = min(l, uf.border(nl).first);
			nr = r = max(r, uf.border(nl).second);
		}
		if (nr < N && (uf.border(nr).first < l || uf.border(nr).second > r))
		{
			safecost += 2 * (nr - r);
			nl = l = min(l, uf.border(nr).first);
			nr = r = max(r, uf.border(nr).second);
		}
		--nl, ++nr;
	} while (L < l || r < R);

	return safecost;
}

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