Submission #54218

#	Time	Username	Problem	Language	Result	Execution time	Memory
54218		radoslav11	Ancient Books (IOI17_books)	C++14	100 / 100	303 ms	87052 KiB

books

#include <bits/stdc++.h>
#include "books.h"
//#include "Lgrader.cpp"

using namespace std;
template<class T, class T2> inline int chkmax(T &x, const T2 &y) { return x < y ? x = y, 1 : 0; }
template<class T, class T2> inline int chkmin(T &x, const T2 &y) { return x > y ? x = y, 1 : 0; }
const int MAXN = (1 << 20);

int n;
int p[MAXN];
bool used[MAXN];

pair<int, int> dfs(int u)
{
	used[u] = true;
	pair<int, int> ret = {u, u};

	if(!used[p[u]])
	{
		pair<int, int> oth = dfs(p[u]);
		chkmax(ret.second, oth.second);
		chkmin(ret.first, oth.first);
	}

	return ret;
}

/*
int L, R;
int mn[1 << 10][1 << 10];
int mx[1 << 10][1 << 10];
int dp[1 << 10][1 << 10];

int Min(int l, int r)
{
	if(l == r) return p[l];
	int &memo = mn[l][r];
	if(memo != -1) return memo;
	return memo = min(Min(l + 1, r), Min(l, r - 1));
}

int Max(int l, int r)
{
	if(l == r) return p[l];
	int &memo = mx[l][r];
	if(memo != -1) return memo;
	return memo = max(Max(l + 1, r), Max(l, r - 1));
}

int rec(int l, int r)
{
	if(l == L && r == R)
		return 0;

	int &memo = dp[l][r];
	if(memo != -1) return memo;

	int nl = Min(l, r);
	if(nl < l) return memo = rec(nl, r);
	
	int nr = Max(l, r);
	if(r < nr) return memo = rec(l, nr);

	memo = (int)1e9;
	if(L < l) chkmin(memo, rec(l - 1, r) + 2);
	if(r < R) chkmin(memo, rec(l, r + 1) + 2);

	return memo;
}*/

int mn[MAXN];
int mx[MAXN];
int lg2[MAXN];

int dist[MAXN];
bool in_queue[MAXN];

long long minimum_walk(std::vector<int> p, int s) 
{
	n = p.size();
	for(int i = 0; i < n; i++)
		::p[i] = p[i];

	int64_t answer = 0;
	for(int i = 0; i < n; i++)
		answer += abs(i - p[i]);

	vector<pair<int, int> > li;
	for(int i = 0; i < n; i++)
		if(i != p[i] && !used[i])
			li.push_back(dfs(i));				
	li.push_back({s, s});

	sort(li.begin(), li.end());
	
	vector<pair<int, int> > tmp;
	for(int i = 0; i < (int)li.size(); i++)
		if(tmp.empty() || tmp.back().second < li[i].first) tmp.push_back(li[i]);
		else chkmax(tmp[tmp.size() - 1].second, li[i].second);

	li = tmp;

	int last = li[0].first;
	for(auto it: li)
	{
		answer += 2 * (it.first - last);
		last = it.second;
	}

	if(s != 0)
	{
		int l, r;
		for(auto it: li)
			if(it.first <= s && s <= it.second)
				l = it.first, r = it.second;

		//memset(mn, -1, sizeof(mn));
		//memset(mx, -1, sizeof(mx));
		//memset(dp, -1, sizeof(dp));
		//answer += rec(s, s);

		mn[s] = mx[s] = p[s];		
		for(int i = s + 1; i <= r; i++) mn[i] = min(mn[i - 1], p[i]);
		for(int i = s + 1; i <= r; i++) mx[i] = max(mx[i - 1], p[i]);
		for(int i = s - 1; i >= l; i--) mn[i] = min(mn[i + 1], p[i]);
		for(int i = s - 1; i >= l; i--) mx[i] = max(mx[i + 1], p[i]);
	
		for(int i = l; i <= r; i++) dist[i] = (int)1e9;

		deque<int> Q;
		Q.push_back(s);
		dist[s] = 0;
		in_queue[s] = 1;

		while(!Q.empty())
		{
			int u = Q.front();
			Q.pop_front();
			in_queue[u] = 0;

			if(chkmin(dist[mn[u]], dist[u]))
			{
				if(!in_queue[mn[u]]) Q.push_front(mn[u]);
				in_queue[mn[u]] = 1;
			}

			if(chkmin(dist[mx[u]], dist[u]))
			{
				if(!in_queue[mx[u]]) Q.push_front(mx[u]);
				in_queue[mx[u]] = 1;
			}
			
			if(u < r && chkmin(dist[u + 1], 2 + dist[u]))
			{
				if(!in_queue[u + 1]) Q.push_back(u + 1);
				in_queue[u + 1] = 1;
			}
	
			if(u > l && chkmin(dist[u - 1], 2 + dist[u]))
			{
				if(!in_queue[u - 1]) Q.push_back(u - 1);
				in_queue[u - 1] = 1;
			}
		}

		answer += min(dist[l], dist[r]);
	}

	return answer;
}

Compilation message (stderr)

books.cpp: In function 'long long int minimum_walk(std::vector<int>, int)':
books.cpp:113:10: warning: 'r' may be used uninitialized in this function [-Wmaybe-uninitialized]
   int l, r;
          ^
books.cpp:113:7: warning: 'l' may be used uninitialized in this function [-Wmaybe-uninitialized]
   int l, r;
       ^

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