Submission #172548

#	Time	Username	Problem	Language	Result	Execution time	Memory
172548		dsjong	Arranging Shoes (IOI19_shoes)	C++14	100 / 100	141 ms	14584 KiB

shoes

#include "shoes.h"
#include <bits/stdc++.h>
using namespace std;
vector<int>pos[200005];
int n;
long long cnt=0;
int get(int x){
	if(x<0) return abs(x)+n;
	return x;
}
int fen[200005];
//add x to idx i
void update(int i,int x){
	for(int j=i;j<=2*n;j+=j&(-j)){
		fen[j]+=x;
	}
}
int query(int i){
	int ans=0;
	for(int j=i;j>0;j-=j&(-j)){
		ans+=fen[j];
	}
	return ans;
}

long long count_swaps(vector<int> s) {
	n=s.size()/2;
	for(int i=0;i<2*n;i++){
		pos[get(s[i])].push_back(i);
	}
	for(int i=1;i<=2*n;i++) reverse(pos[i].begin(),pos[i].end());
	memset(fen,0,sizeof fen);
	for(int i=1;i<=2*n;i++) update(i,1);
	for(int i=0;i<2*n;i++){
		//cout<<i<<": ";
		if(pos[get(s[i])].empty()||pos[get(s[i])].back()>i) continue;
		pos[get(s[i])].pop_back();
		int j=pos[get(-s[i])].back();
		pos[get(-s[i])].pop_back();
		int posj=query(j), posi=query(i);
		if(s[i]<0){
			cnt+=posj-posi-1;
			update(i+1,1);
			update(j+1,-1);
		}
		else{
			cnt+=posj-posi;
			update(i+1,1);
			update(j+1,-1);
		}
		//cout<<cnt<<endl;
	}
	return cnt;
}

• Subtask 1: 10 / 10
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 15 / 15
• Subtask 5: 20 / 20
• Subtask 6: 15 / 15