Submission #838232

#	Time	Username	Problem	Language	Result	Execution time	Memory
838232		Johann	Ancient Books (IOI17_books)	C++14	50 / 100	153 ms	28028 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;

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);
	cycle(P[i], mini, maxi, cycleCnt);
}

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];

	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;
	}

	vi maxL(N, s), maxR(N, s), cost(N, 0);
	if (vis[s] != -1)
		tie(maxL[s], maxR[s]) = borders[vis[s]];
	for (int i = s + 1; i < N; ++i)
	{
		maxL[i] = maxL[i - 1], maxR[i] = maxR[i - 1], cost[i] = cost[i - 1];
		if (maxR[i] < i)
			cost[i] += 2, maxR[i] = i;
		if (vis[i] != -1)
			maxL[i] = min(maxL[i], borders[vis[i]].first),
			maxR[i] = max(maxR[i], borders[vis[i]].second);
	}
	for (int i = s - 1; i >= 0; --i)
	{
		maxL[i] = maxL[i + 1], maxR[i] = maxR[i + 1], cost[i] = cost[i + 1];
		if (maxL[i] > i)
			cost[i] += 2, maxL[i] = i;
		if (vis[i] != -1)
			maxL[i] = min(maxL[i], borders[vis[i]].first),
			maxR[i] = max(maxR[i], borders[vis[i]].second);
	}

	ll mincost = INF;
	int l = s, r = N - 1;
	while (l >= 0 && r >= 0)
	{
		int virtualL = min(maxL[l], maxL[maxL[r]]);
		if (max(maxR[l], maxR[r]) < R || virtualL > L)
			--l;
		else
		{
			ll tmp = safecost + cost[r];
			if (l < maxL[r])
				tmp += cost[l] - cost[maxL[r]];
			mincost = min(mincost, tmp);
			--r;
		}
	}

	return mincost;
}

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