Submission #608249

#	Time	Username	Problem	Language	Result	Execution time	Memory
608249		Hanksburger	Arranging Shoes (IOI19_shoes)	C++17	100 / 100	73 ms	15632 KiB

shoes

#include "shoes.h"
#include <bits/stdc++.h>
using namespace std;
int sum[200005], r[200005];
vector<int> pos[200005];
void update(int x, int y)
{
    for (int i=x; i<=200000; i+=i&(-i))
        sum[i]+=y;
}
int query(int x)
{
    int ans=0;
    for (int i=x; i; i-=i&(-i))
        ans+=sum[i];
    return ans;
}
long long count_swaps(vector<int> v)
{
    int n=v.size()/2, cnt=0;
    for (int i=0; i<n*2; i++)
        pos[v[i]+n].push_back(i);
    long long ans=0;
    for (int i=0; i<n; i++)
    {
        for (int j=0; j<pos[i].size(); j++)
        {
            if (pos[i][j]>pos[n*2-i][j])
            {
                swap(pos[i][j], pos[n*2-i][j]);
                ans++;
            }
            cnt++;
            v[pos[i][j]]=-cnt;
            v[pos[n*2-i][j]]=cnt;
            r[pos[i][j]]=pos[n*2-i][j];
        }
    }
    for (int i=0; i<n*2; i++)
    {
        if (v[i]>0)
            update(i, -1);
        else
        {
            update(r[i], 1);
            ans+=r[i]-i-query(r[i]);
        }
    }
    return ans;
}

Compilation message (stderr)

shoes.cpp: In function 'long long int count_swaps(std::vector<int>)':
shoes.cpp:26:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   26 |         for (int j=0; j<pos[i].size(); j++)
      |                       ~^~~~~~~~~~~~~~

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