Submission #69601

#	Time	Username	Problem	Language	Result	Execution time	Memory
69601		Noam527	Ancient Books (IOI17_books)	C++17	100 / 100	525 ms	226596 KiB

books

#include "books.h"
#include <bits/stdc++.h>
#define endl '\n'
#define fast ios::sync_with_stdio(0), cin.tie(0), cout.tie(0)
#define debug cout << "ok" << endl
#define finish(x) return cout << x << endl, 0
typedef long long ll;
typedef long double ldb;
const int md = 1e9 + 7, inf = 1e9 + 7;
const ll hs = 199;
const ldb eps = 1e-9, pi = acos(-1);
using namespace std;

int n;
vector<int> a, vis, to;

int cycle(int st) {
	vis[st] = 1;
	int rtn = st;
	st = a[st];
	while (!vis[st]) {
		rtn = max(rtn, st);
		vis[st] = 1;
		st = a[st];
	}
	return rtn;
}
vector<int> cycle2(int st) {
	vis[st] = 1;
	vector<int> rtn = { st };
	st = a[st];
	while (!vis[st]) {
		rtn.push_back(st);
		vis[st] = 1;
		st = a[st];
	}
	return rtn;
}

ll minimum_walk(vector<int> p, int s) {
	n = p.size();
	a = p;
	ll sum = 0;
	for (int i = 0; i < n; i++)
		sum += abs(i - a[i]);

	int l = 0, r = n - 1;
	while (l < n && a[l] == l) l++;
	if (l == n) return 0;
	while (a[r] == r) r--;



	vis.resize(n, 0);
	to.resize(n, -1);
	for (int i = l; i <= r; i++)
		if (!vis[i])
			to[i] = cycle(i);
	vector<pair<int, int>> st, range(n);
	for (int i = l; i <= r; i++)
		if (to[i] != -1) {
			if (!st.size()) st.push_back({ i, to[i] });
			else {
				if (st.back().second < i) st.push_back({ i, to[i] });
				else st.back().second = max(st.back().second, to[i]);
			}
		}

	ll rtn = sum + 2LL * ((int)st.size() - 1);
	if (s < l) return rtn + 2 * (l - s);
	if (r < s) return rtn + 2 * (s - r);

	for (auto &i : vis) i = 0;
	vector<int> tmp;
	queue<int> q;
	int optl, optr, x;
	for (const auto &i : st) {
		if (i.first <= s && s <= i.second) {
			ll add = 0;
			for (int j = i.first; j <= i.second; j++) {
				if (!vis[j]) {
					tmp = cycle2(j);
					for (const auto &ind : tmp)
						range[ind] = { j, to[j] };
				}
			}
			q.push(s);
			optl = optr = s;
			while (optl != i.first || optr != i.second) {
				while (!q.empty()) {
					x = q.front(), q.pop();
					if (range[x].first < optl || optr < range[x].second) {
						for (int j = range[x].first; j < optl; j++)
							q.push(j);
						for (int j = optr + 1; j <= range[x].second; j++)
							q.push(j);
						optl = min(optl, range[x].first);
						optr = max(optr, range[x].second);
					}
				}
				if (optl != i.first || optr != i.second) {
					add++;
					if (i.first < optl) q.push(optl - 1), optl--;
					if (optr < i.second) q.push(optr + 1), optr++;
				}
			}
			return rtn + 2 * add;
		}
	}
}

Compilation message (stderr)

books.cpp: In function 'll minimum_walk(std::vector<int>, int)':
books.cpp:110:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^

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