Submission #294940

#	Time	Username	Problem	Language	Result	Execution time	Memory
294940		amoo_safar	Ancient Books (IOI17_books)	C++17	100 / 100	364 ms	36104 KiB

books

#include "books.h"

#include <bits/stdc++.h>

#define pb push_back
#define F first
#define S second
#define all(x) x.begin(), x.end()

using namespace std;

typedef pair<int, int> pii;
typedef long long ll;

const int N = 1e6 + 10;

int mk[N], mk2[N];
int L[N], R[N];
//int mn[N][N], mx[N][N];
//ll dp[N][N];

ll minimum_walk(vector<int> p, int s) {
	int n = p.size();
	ll ans = 0;
	ll near = n;
	for(int i = 0; i < n; i++){
		if(p[i] != i){
			ans += abs(p[i] - i);
		} else {
			//mk[i] = 1;
			R[i] = i;
			L[i] = i;
		}
	}
	cerr << "# " << ans << '\n';
	mk[s] = 0;
	int st = 0, en = n - 1;
	while(p[st] == st && st < s){ mk[st] = 1; st ++; }
	while(p[en] == en && en > s){ mk[en] = 1; en --; }

	int com = 0;
	vector<pii> seg;
	for(int i = st; i < en; i++){
		if(mk[i]) continue;
		com ++;
		vector<int> vis;
		int nw = i;
		while(!mk[nw]){
			mk[nw] = 1;
			vis.pb(nw);
			nw = p[nw];
		}
		sort(all(vis));
		seg.pb({vis[0], vis.back()});
		for(auto x : vis) L[x] = vis[0];
		for(auto x : vis) R[x] = vis.back();
	}
	if(com == 0) return 0;
	sort(all(seg));
	int mxr = st;
	for(int i = 0; i < (int)seg.size(); i++){
		if(mxr < seg[i].F)
			mk2[mxr] = 1, ans += 2;
		mxr = max(mxr, seg[i].S);
	}
	mk2[mxr] = 1;
	/*
	for(int i = 0; i < n; i++) mn[i][i] = L[i];
	for(int i = 0; i < n; i++) mx[i][i] = R[i];
	for(int ln = 1; ln < n; ln ++){
		for(int i = 0; i + ln < n; i++){
			int j = i + ln;
			mn[i][j] = min(mn[i][j - 1], mn[i + 1][j]);
			mx[i][j] = max(mx[i][j - 1], mx[i + 1][j]);
		}
	}
	*/
	//if(ans == 0) return 0;

	int nwl = s;
	int nwr = s;
	int mxl = L[s];
	mxr = R[s];
	cerr << ans << '\n';
	while(!mk2[nwr]){
		/*
		mxl = L[nwl];
		for(int i = nwl; i <= nwr; i ++) mxl = min(mxl, L[i]);
		mxr = R[nwl];
		for(int i = nwl; i <= nwr; i ++) mxr = max(mxr, R[i]);
		*/
		//cerr << "! " << nwl << ' ' << nwr << ' ' << l2 << ' ' << r2 << '\n';
		
		int l2 = mxl;
		int r2 = mxr;
		
		if(pii(l2, r2) == pii(nwl, nwr) && !mk2[r2]){
			ans += 2;
			l2 --;
			r2 ++;
		}
		while(nwl > l2){nwl --; mxl = min(mxl, L[nwl]), mxr = max(mxr, R[nwl]);}
		while(nwr < r2){nwr ++; mxl = min(mxl, L[nwr]), mxr = max(mxr, R[nwr]);}
		//nwl = l2;
		//nwr = r2;
	}

	return ans;
}
/*
4 1
0 3 1 2

*/

Compilation message (stderr)

books.cpp: In function 'll minimum_walk(std::vector<int>, int)':
books.cpp:25:5: warning: unused variable 'near' [-Wunused-variable]
   25 |  ll near = n;
      |     ^~~~

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