Submission #1104927

#	Time	Username	Problem	Language	Result	Execution time	Memory
1104927		alexander707070	Ancient Books (IOI17_books)	C++14	50 / 100	107 ms	16984 KiB

books

#include<bits/stdc++.h>
#define MAXN 1000007
using namespace std;

int n,s,p[MAXN],fr,last,mins,maxs,pref[MAXN],curr;
bool li[MAXN];
long long ans;

void dfs(int x){
	li[x]=true;

	ans+=abs(x-p[x]);
	mins=min(mins,x);
	maxs=max(maxs,x);

	if(!li[p[x]])dfs(p[x]);
}

long long minimum_walk(vector<int> P, int S){
	n=int(P.size()); s=S+1;

	for(int i=1;i<=n;i++){
		p[i]=P[i-1]+1;
	}
	last=0; fr=n+1;

	for(int i=1;i<=n;i++){
		if(!li[i]){
			if(p[i]!=i)last=i;

			mins=n; maxs=1;
			dfs(i);

			pref[mins]++; pref[maxs]--;
		}
	}

	for(int i=1;i<=n;i++)li[i]=false;

	for(int i=n;i>=1;i--){
		if(!li[i]){
			if(p[i]!=i)fr=i;
			dfs(i);
		}
	}
	ans/=2;

	for(int i=1;i<=n-1;i++){
		curr+=pref[i];
		if(i<s)continue;

		if(curr==0 and last>i)ans+=2;
	}

	curr=0;
	for(int i=n;i>=1;i--){
		curr+=pref[i];
		if(i>s)continue;
		if(curr==0 and fr<i)ans+=2;
	}

	return ans;
}

/*int main(){

	cout<<minimum_walk({0, 2, 3, 1}, 0)<<"\n";

	return 0;
}*/

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