Submission #1083272

#	Time	Username	Problem	Language	Result	Execution time	Memory
1083272		Math4Life2020	Ancient Books (IOI17_books)	C++17	50 / 100	97 ms	39508 KiB

books

#include <bits/stdc++.h>
using namespace std;

using ll = long long; using pii = pair<ll,ll>;
const ll INF = 1e8;
//#include "books.h"

ll minimum_walk(vector<int> p, int s) {
	ll N = p.size();
	ll flux[N];
	for (ll i=0;i<N;i++) {
		flux[i]=0;
	}
	for (ll i=0;i<N;i++) {
		if (p[i]>i) {
			flux[i]++;
			flux[p[i]]--;
		}
	}
	ll pf[N+1];
	pf[0]=0;
	ll ans = 0;
	for (ll i=0;i<N;i++) {
		pf[i+1]=pf[i]+flux[i];
		//cout << "x="<<(i+1)<<", pf[x]="<<pf[i+1]<<"\n";
		if (pf[i+1]>1) {
			ans += 2*(pf[i+1]-1);
		}
	}
	ll maxl[N+1]; ll minl[N+1];
	for (ll i=0;i<=N;i++) {
		maxl[i]=-INF;
		minl[i]=INF;
	}
	for (ll i=1;i<=N;i++) {
		maxl[pf[i]]=max(maxl[pf[i]],i);
		minl[pf[i]]=min(minl[pf[i]],i-1);
	}
	for (ll i=N;i>=1;i--) {
		maxl[i-1]=max(maxl[i],maxl[i-1]);
		minl[i-1]=min(minl[i],minl[i-1]);
	}
	//ll xc = 0;
	/*for (ll i=1;i<=N;i++) {
		//cout << "i="<<i<<", maxl="<<maxl[i]<<", minl="<<minl[i]<<"\n"; 
		if (minl[i]!=INF) {
			//ans += abs(xc-minl[i]);
			//xc = minl[i];
			//ans += abs(xc-maxl[i]);
			//xc = maxl[i];
			ans += 2*(maxl[i]-minl[i]);
			if (i==1) {
				if (s<minl[i]) {
					ans += 2*(minl[i]-s);
				} else if (s>maxl[i]) {
					ans += 2*(maxl[i]-s);
				}
			}
		}
	}*/
	if (minl[1]!=INF) { //valid if s=0
		ans += 2*(maxl[1]-minl[1]);
		/*if (s<minl[1]) {
			ans += 2*(minl[1]-s);
		} else if (s>maxl[1]) {
			ans += 2*(s-maxl[1]);
		}*/
		ll MD = INF;
		for (ll i=0;i<N;i++) {
			if (p[i]!=i) {
				MD = min(MD,abs(s-i));
			}
		}
		ans += 2*MD;
	}
	//cout << "minl[1],maxl[1]="<<minl[1]<<","<<maxl[1]<<"\n";
	//ans += abs(xc);
	return ans;
}

/*int main() {
	vector<int> p1 = {0,1,4,3,2,5,6};
	cout << minimum_walk(p1,3);
}*/

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