Submission #1082991

#	Time	Username	Problem	Language	Result	Execution time	Memory
1082991		happypotato	Ancient Books (IOI17_books)	C++17	50 / 100	114 ms	26848 KiB

books

#include "books.h"
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int, int>
#define ff first
#define ss second
#define pb push_back
long long st123(vector<int> p, int s) {
	vector<int> ori = p;
	int n = (int)(p.size());
	ll ans = 0;
	for (int i = 0; i < n; i++) {
		if (p[i] == -1 || p[i] == i) continue;
		int cur = i;
		vector<int> seq = {cur};
		while (p[cur] != i) {
			cur = p[cur];
			seq.pb(cur);
		}
		// cerr << i << ": ";
		// for (int x : seq) cerr << x << ' ';
		// cerr << endl;
		for (int i = 0; i < (int)(seq.size()); i++) {
			ans += abs(seq[(i + 1) % (int)(seq.size())] - seq[i]);
			p[seq[i]] = -1;
		}
	}
	vector<int> bruh;
	int maxi = 0;
	for (int i = 0; i < n; i++) {
		maxi = max(maxi, ori[i]);
		if (maxi == i) bruh.pb(i);
	}
	// for (int x : bruh) cerr << x << ' ';
	// cerr << endl;
	while (bruh.size() >= 2) {
		int x = bruh.size();
		if (bruh[x - 1] - bruh[x - 2] == 1) {
			bruh.pop_back();
		} else break;
	}
	ans += ((int)(bruh.size()) - 1) * 2;
	return ans;
}
long long minimum_walk(vector<int> p, int s) {
	if (s == 0) return st123(p, s);
	vector<int> ori = p;
	int n = (int)(p.size());
	ll ans = 0;
	vector<pii> range(n);
	for (int i = 0; i < n; i++) {
		if (p[i] == -1) continue;
		int cur = i;
		vector<int> seq = {cur};
		while (p[cur] != i) {
			cur = p[cur];
			seq.pb(cur);
		}
		pii get = {i, i};
		for (int x : seq) {
			get.ff = min(get.ff, x);
			get.ss = max(get.ss, x);
		}
		// cerr << "seq: ";
		// for (int x : seq) cerr << x << ' ';
		// cerr << " | " << get.ff << ' ' << get.ss << endl;
		for (int j = 0; j < (int)(seq.size()); j++) {
			ans += abs(seq[(j + 1) % (int)(seq.size())] - seq[j]);
			range[seq[j]] = get;
			p[seq[j]] = -1;
		}
	}
	// for (int i = 0; i < n; i++) {
	// 	cerr << i << ": " << range[i].ff << ' ' << range[i].ss << endl;
	// }

	vector<vector<int>> dp(n);
	for (int i = 0; i < n; i++) dp[i].resize(n, 1e9);
	queue<pii> q;
	for (int i = range[s].ff; i <= range[s].ss; i++) {
		for (int j = i; j <= range[s].ss; j++) {
			dp[i][j] = 0;
			q.push({i, j});
		}
	}
	while (!q.empty()) {
		pii cur = q.front(); q.pop();
		if (cur.ff > 0) {
			pii nrange = {range[cur.ff - 1].ff, max(cur.ss, range[cur.ff - 1].ss)};
			if (dp[nrange.ff][nrange.ss] > dp[cur.ff][cur.ss] + 1) {
				dp[nrange.ff][nrange.ss] = dp[cur.ff][cur.ss] + 1;
				q.push(nrange);
			}
		}
		if (cur.ss < n - 1) {
			pii nrange = {min(cur.ff, range[cur.ss + 1].ff), range[cur.ss + 1].ss};
			if (dp[nrange.ff][nrange.ss] > dp[cur.ff][cur.ss] + 1) {
				dp[nrange.ff][nrange.ss] = dp[cur.ff][cur.ss] + 1;
				q.push(nrange);
			}
		}
	}
	int lb = 0, rb = n - 1;
	while (lb < n && ori[lb] == lb) lb++;
	if (lb == n) return 0;
	while (rb >= 0 && ori[rb] == rb) rb--;
	int take = 1e9;
	for (int i = 0; i <= lb; i++) {
		for (int j = rb; j < n; j++) take = min(take, dp[i][j]);
	}
	ans += take * 2;
	return ans;
}

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