Submission #986143

#	Time	Username	Problem	Language	Result	Execution time	Memory
986143		mariaclara	Ancient Books (IOI17_books)	C++17	100 / 100	143 ms	58676 KiB

books

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

using namespace std;

typedef long long ll;
typedef pair<int,int> pii;
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
#define mk make_pair
#define pb push_back
#define fr first
#define sc second

ll minimum_walk(vector<int> p, int s) {
	int n = sz(p), L = n, R = -1;
	vector<int> l(n), r(n);
	vector<bool> vis(n,0);
	vector<pii> aux, range;

	ll ans = 0;
	for(int i = 0; i < n; i++) {
		int x = i, m = i;
		vector<int> cicle;
		while(!vis[x]) {
			vis[x] = 1;
			cicle.pb(x);
			x = p[x];
			m = max(m, x);
		}

		for(int it : cicle) l[it] = i, r[it] = m;

		ans += abs(p[i]-i);
		aux.pb({i,m});
		if(i != m or i == s) L = min(L,i), R = max(R,m);
	}

	for(int i = 0; i < sz(aux);) {
		int l = aux[i].fr, r = aux[i].sc, j = i;
		while(j < sz(aux) and aux[j].fr <= r) {
			r = max(r, aux[j].sc);
			j++;
		}
		i=j;
		range.pb({l,r});
	}

	for(int i = 1; i < sz(range); i++)
		if(range[i-1].fr >= L and range[i].sc <= R)
			ans += 2*(range[i].fr - range[i-1].sc);

	vector<pii> a(n), b(n);
	for(int i = 1; i < n; i++) {
		if(l[i-1] <= l[i]) {
			a[i] = mk(i-1, max(0,l[i] - i + 1));
			continue;
		}
		a[i].fr = a[i-1].fr;
		while(l[a[i].fr] > l[i]) a[i].fr = a[a[i].fr].fr;
		a[i].sc = max(0, l[i] - a[i].fr);
	}

	b[n-1] = mk(n-1,0);
	for(int i = n-2; i >= 0; i--) {
		if(r[i+1] >= r[i]) {
			b[i] = mk(i+1, max(0,i+1 - r[i]));
			continue;
		}
		b[i].fr = b[i+1].fr;
		while(r[b[i].fr] < r[i]) b[i].fr = b[b[i].fr].fr;
		b[i].sc = max(0, b[i].fr - r[i]);
	}

	vector<int> dist(n, n);
	deque<int> fila;
	fila.emplace_front(s);
	dist[s] = 0;
	vis.clear();
	vis.resize(n,0);

	while(!fila.empty()) {
		int x = fila.front();
		fila.pop_front();

		if(vis[x]) continue;
		vis[x] = 1;

		if(dist[a[x].fr] > dist[x] + a[x].sc) {
			if(a[x].sc == 0) fila.emplace_front(a[x].fr);
			else fila.emplace_back(a[x].fr);
			dist[a[x].fr] = dist[x] + a[x].sc;
		}
		if(dist[b[x].fr] > dist[x] + b[x].sc) {
			if(b[x].sc == 0) fila.emplace_front(b[x].fr);
			else fila.emplace_back(b[x].fr);
			dist[b[x].fr] = dist[x] + b[x].sc;
		}
	}

	for(int i = 0; i < sz(range); i++) 
		if(range[i].sc >= s) { R = range[i].sc; break; }

	return ans + 2*dist[R];
}

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