Submission #597899

#	Time	Username	Problem	Language	Result	Execution time	Memory
597899		Hanksburger	Arranging Shoes (IOI19_shoes)	C++17	100 / 100	62 ms	15308 KiB

shoes

#include "shoes.h"
#include <bits/stdc++.h>
using namespace std;
int a[200005], pos2[200005], n, cnt;
vector<int> pos[200005];
void upd(int x)
{
    for (int i=x; i<n*2; i+=i&(-i))
        a[i]++;
}
int qry(int x)
{
    int sum=0;
    for (int i=x; i; i-=i&(-i))
        sum+=a[i];
    return sum;
}
long long count_swaps(vector<int> v)
{
	n=cnt=v.size()/2;
	for (int i=0; i<n*2; i++)
        pos[v[i]+n].push_back(i);
    long long ans=0;
    for (int i=1; i<=n; i++)
    {
        for (int j=0; j<pos[n+i].size(); j++)
        {
            if (j)
            {
                v[pos[n+i][j]]=++cnt;
                v[pos[n-i][j]]=-cnt;
            }
            if (pos[n+i][j]<pos[n-i][j])
            {
                swap(v[pos[n+i][j]], v[pos[n-i][j]]);
                ans++;
            }
        }
    }
    for (int i=0; i<n*2; i++)
        if (v[i]>0)
            pos2[v[i]]=i;
    for (int i=0; i<n*2; i++)
    {
        if (v[i]<0)
        {
            int p=pos2[-v[i]];
            ans+=p-i-1-qry(p)+qry(i);
            upd(p);
        }
    }
    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[n+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