Submission #624659

#	Time	Username	Problem	Language	Result	Execution time	Memory
624659		8e7	Ancient Books (IOI17_books)	C++17	100 / 100	136 ms	27780 KiB

books

//Challenge: Accepted
#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
#ifdef zisk
void debug(){cout << endl;}
template<class T, class ... U> void debug(T a, U ...b){cout << a << " ", debug(b...);}
template<class T> void pary(T l, T r) {
	while (l != r) cout << *l << " ", l++;
	cout << endl;
}
#else
#define debug(...) 0
#define pary(...) 0
#endif
#define ll long long
#define maxn 1000005
#define pii pair<int, int>
#define ff first
#define ss second
#include "books.h"

const int inf = 1e9;
pii ran[maxn], color[maxn];
long long minimum_walk(vector<int> p, int s) {
	ll ans = 0;
	int n = p.size();
	vector<int> a(n, 0);
	vector<bool> vis(n);
	{
		int c = 0;
		for (int i = 0;i < n;i++) {
			ans += abs(p[i] - i);
			if (!vis[i]) {
				c++;
				int cur = i;
				int mi = inf, ma = 0;
				do {
					mi = min(mi, cur);
					ma = max(ma, cur);
					a[cur] = c;
					vis[cur] = 1;
					cur = p[cur];
				} while (!vis[cur]);
				color[c] = {mi, ma};
			}
		}
		for (int i = 0;i < n;i++) ran[i] = color[a[i]];
	}

	int lb = 0, rb = n-1;
	while (lb < s && p[lb] == lb) lb++;
	while (rb > s && p[rb] == rb) rb--;
	auto expand = [&] (int l, int r, int nl, int nr, int type) { //0:none, 1:left, 2:right
		if (type == 1) {
			l = max(lb, l-1);
			nl = min(nl, ran[l].ff);	
			nr = max(nr, ran[l].ss);
		} else if(type == 2) {
			r = min(rb, r+1);
			nl = min(nl, ran[r].ff);	
			nr = max(nr, ran[r].ss);
		}
		while (nl < l || nr > r) {
			while (nl < l) {
				l--;	
				nl = min(nl, ran[l].ff);
				nr = max(nr, ran[l].ss);
			}
			while (nr > r) {
				r++;
				nl = min(nl, ran[r].ff);
				nr = max(nr, ran[r].ss);
			}
		}
		return make_pair(l, r);
	};
	pii cur = {s, s};	
	cur = expand(s, s, ran[s].ff, ran[s].ss, 0);	
	while (cur.ff > lb || cur.ss < rb) {
		if (cur.ff == lb) {
			cur = expand(cur.ff, cur.ss, cur.ff, cur.ss, 2);
			ans+=2;
		} else if (cur.ss == rb){
			cur = expand(cur.ff, cur.ss, cur.ff, cur.ss, 1);
			ans+=2;
		} else {
			pii tmp = cur, lef;
			int sl = 0, sr = 0, vl, vr;
			while (tmp.ss <= cur.ss) {
				tmp = expand(tmp.ff, tmp.ss, tmp.ff, tmp.ss, 1);
				sl++;
				if (tmp.ff == lb) break;
			}
			vl = sl;
			if (tmp.ss <= cur.ss) vl = inf;
			lef = tmp;

			tmp = cur;	
			while (tmp.ff >= cur.ff) {
				tmp = expand(tmp.ff, tmp.ss, tmp.ff, tmp.ss, 2);
				sr++;
				if (tmp.ss == rb) break;
			}
			vr = sr;
			if (tmp.ff >= cur.ff) vr = inf;
			if (vl == inf && vr == inf) {
				ans += 2 * (sl + sr);
				break;
			} else if (vl < vr) {
				ans += 2 * vl;
				cur = lef;
			} else {
				ans += 2 * vr;
				cur = tmp;
			}
		}
	}
	return ans;
}

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