Submission #941987

#	Time	Username	Problem	Language	Result	Execution time	Memory
941987		beaboss	Ancient Books (IOI17_books)	C++14	50 / 100	95 ms	19028 KiB

books

// Source: https://oj.uz/problem/view/IOI17_books
// 
#include "books.h"


#include "bits/stdc++.h"

using namespace std;

#define s second
#define f first
#define pb push_back

typedef long long ll;

typedef pair<ll, ll> pii;
typedef vector<pii> vpii;

typedef vector<ll> vi;

#define FOR(i, a, b) for (ll i = (a); i<b; i++)

bool ckmin(ll& a, ll b){ return b < a ? a = b, true : false; }

bool ckmax(ll& a, ll b){ return b > a ? a = b, true : false; }

const ll N = 1e6 + 10;
ll ri[N], le[N];
bool vis[N];
vector<int> nxt;
ll n;
ll l,r ;

void extend() {
	ll LL = nxt[l];
	while (LL < l && l > 0) {
		l--;
		LL = min(LL, (ll) nxt[l]);
	}
	ll rr = nxt[r];
	while (r < rr && r < n-1) {
		r++;
		rr = max(rr, (ll)nxt[r]);
	}
}

ll minimum_walk(vector<int> p, int s) {
	n = p.size();
	l = r = s;
	nxt = p;
	ll ans = 0;
	FOR(i, 0, n) ans += abs(i - p[i]);

	ll st = 0;
	for (;st < n;st++) if (p[st] != st) break;
	ll en = n-1;
	for (;en >= 0;en--) if (p[en] != en) break;
	
	if (st >= en) return 0;

	while (l > st || r < en) {
		extend();
		// cout << l << r << endl;
		ll lo = l;
		ll ro = r;

		ll cr = 0;
		while (l == lo && r < en) {
			cr+=2;r++;
			// cout << 'd' << endl;
			extend();
		}
		bool rw = (nxt[r] < l);

		ll fl = l, fr=r;

		l = lo;r = ro;

		ll cl = 0;
		while (r == ro && l > st) {
			// cout << l << endl;
			cl+=2;l--;extend();
		}
		// cout << 'd' << endl;

		bool lw = (nxt[l] > r);

		l = min(l, fl);
		r = max(r, fr);

		// assert(lw ^ rw);
		if (!lw || !rw) {
			ans += cl + cr;
			break;
		}
		ans += min(cl, cr);
	}

	return ans;

}



// int main() {
// 	ios::sync_with_stdio(false);
// 	cin.tie(nullptr);

// 	// FOR(i, 0, 8) {
// 	// mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
// 	// ll n = 100;
// 	// vi here(n);
// 	// FOR(i, 0, n) here[i] = i;
// 	// shuffle(here.begin(), here.end(), rng);
// 	// FOR(i, 0, n) cout << here[i] << ' ';
// 	// cout << endl;


// 	ll res = minimum_walk({0, 2, 4, 5, 1, 6, 3}, 0);
// 	cout << res << endl;

// }

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