Submission #855819

#	Time	Username	Problem	Language	Result	Execution time	Memory
855819		dong_liu	Arranging Shoes (IOI19_shoes)	C++17	100 / 100	53 ms	14672 KiB

shoes

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

#define ar array
#define sz(v) int(v.size())

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

struct FT {
	vector<int> t;
	FT(int n) : t(n,0) {}
	
	void upd(int i, int x) {
		while (i < sz(t)) {
			t[i] += x;
			i |= i+1;
		}
	}
	int qry(int i) {
		int x = 0;
		while (i >= 0) {
			x += t[i];
			i &= i+1, i--;
		}
		return x;
	}
	int qry(int l, int r) {
		return qry(r)-qry(l-1);
	}
};

ll count_swaps(vector<int> v) {
	int n = sz(v) / 2;
	vector<vector<int>> L(n), R(n);
	for (int i = 0; i < n*2; i++)
		if (v[i]<0) L[abs(v[i])-1].push_back(i);
		else R[abs(v[i])-1].push_back(i);
	vector<pi> f;
	for (int a = 0; a < n; a++) {
		assert(sz(L[a]) == sz(R[a]));
		for (int j = 0; j < sz(L[a]); j++)
			f.push_back({L[a][j],R[a][j]});
	}
	ll ans = 0;
	for (auto &[l,r] : f) {
		if (l>r) {
			swap(l,r);
			ans++;
		}
	}
	sort(f.begin(), f.end());
	FT ft(n*2);
	for (auto [l,r] : f) {
		ans += ft.qry(l,n*2-1)+ft.qry(r,n*2-1);
		ft.upd(r,1);
	}
	return ans;
}
// int main() {
// 	cout << count_swaps({2,1,-1,-2}) << '\n';
// 	cout << count_swaps({-2,2,2,-2,-2,2}) << '\n';
// }

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