Submission #227950

#	Time	Username	Problem	Language	Result	Execution time	Memory
227950		staniewzki	Arranging Shoes (IOI19_shoes)	C++17	100 / 100	170 ms	14840 KiB

shoes

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

struct Fenwick {
	vector<int> tree;
	Fenwick(int n) : tree(n + 1) {}
	void update(int pos, int val) {
		for(pos++; pos < size(tree); pos += (pos & -pos))
			tree[pos] += val;
	}
	int query(int pos) {
		int ret = 0;
		for(pos++; pos > 0; pos -= (pos & -pos)) 
			ret += tree[pos];
		return ret;
	}
	int query(int l, int r) {
		return query(r) - query(l - 1);
	}
};

long long count_swaps(vector<int> s) {
	int m = size(s), n = m / 2;
	vector<vector<int>> pos(m + 1);
	for(int i = m - 1; i >= 0; i--)
		pos[n + s[i]].emplace_back(i);

	long long ans = 0;
	Fenwick tree(m);
	for(int i = 0; i < m; i++) {
		if(!tree.query(i, i)) {
			int j = pos[n - s[i]].back();
			ans += j - (i + 1) - tree.query(i, j) + (s[i] > 0);
			tree.update(j, +1);
			pos[n - s[i]].pop_back();
			pos[n + s[i]].pop_back();
		}
	}	
	return ans;
}

Compilation message (stderr)

shoes.cpp: In member function 'void Fenwick::update(int, int)':
shoes.cpp:10:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(pos++; pos < size(tree); pos += (pos & -pos))
              ~~~~^~~~~~~~~~~~

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