Submission #1204936

#	Time	Username	Problem	Language	Result	Execution time	Memory
1204936		HasanV11010238	Ancient Books (IOI17_books)	C++20	42 / 100	144 ms	23880 KiB

books

#include "books.h"
#include <bits/stdc++.h>
#define ll long long
#define INF 1000000000000000
using namespace std;
vector<int> vis, to, ml, mr;
int le, ri;
void dfs(int x){
	le = min(le, x);
	ri = max(ri, x);
	vis[x] = 1;
	if (vis[to[x]] == 0) dfs(to[x]);
}
void ass(int x, int va1, int va2){
	ml[x] = va1;
	mr[x] = va2;
	vis[x] = 2;
	if (vis[to[x]] == 1) ass(to[x], va1, va2);
}

long long minimum_walk(std::vector<int> p, int s) {
	int n = p.size();
	ll ans = 0;
	for (int i = 0; i < n; i++){
		ans += abs(i - p[i]);
	}
	to = p;
	vis.assign(n, 0), ml.assign(n, 0), mr.assign(n, 0);
	for (int i = 0; i < n; i++){
		if (vis[i] == 0){
			le = n, ri = 0;
			dfs(i);
			ass(i, le, ri);
		}
	}
	int l = 0, r = n - 1;
	while (l < s && to[l] == l) l++;
	while (r > s && to[r] == r) r--;
	if (l > r) return 0;
	if (n <= 1000){
		vector<vector<ll>> dp(n, vector<ll>(n, INF));
		vector<vector<int>> mi(n, vector<int>(n, n)), ma(n, vector<int>(n, 0));
		for (int i = 0; i < n; i++){
			mi[i][i] = ml[i], ma[i][i] = mr[i];
			for (int j = i + 1; j < n; j++){
				mi[i][j] = min(mi[i][j - 1], ml[j]);
				ma[i][j] = max(ma[i][j - 1], mr[j]);
			}
		}
		dp[s][s] = 0;
		for (int ga = 0; ga < n; ga++){
			for (int i = 0, j = ga; j < n; i++, j++){
				dp[mi[i][j]][ma[i][j]] = min(dp[mi[i][j]][ma[i][j]], dp[i][j]);
				if (i != 0){
					dp[i - 1][j] = min(dp[i - 1][j], dp[i][j] + 2);
				}
				if (j != n - 1){
					dp[i][j + 1] = min(dp[i][j + 1], dp[i][j] + 2);
				}
			}
		}
		return dp[l][r] + ans;
	}
	int tt;
	for (int i = 0; i < r; i++){
		if (tt < i) ans += 2;
		tt = max(tt, mr[i]);
	}
	return ans;
}

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