Submission #850064

#	Time	Username	Problem	Language	Result	Execution time	Memory
850064		Bach21	Arranging Shoes (IOI19_shoes)	C++14	100 / 100	70 ms	12832 KiB

shoes

#include <bits/stdc++.h>
#include "shoes.h"
using namespace std;
const int nmax=2e5+5;
int BIT[nmax];
void update(int s,int val)
{
    for (int i=s;i<nmax;i+=i&-i)
    {
        BIT[i]+=val;
    }
}
int query(int s)
{
    int res=0;
    for (int i=s;i;i-=i&(-i))
    {
        res+=BIT[i];
    }
    return res;
}
long long count_swaps(vector<int> s)
{
    long long res=0;
    int n=(int)(s.size()/2);
    vector<pair<int,int>> v[nmax];
    for (int i=0;i<s.size();i++)
    {
        v[abs(s[i])].push_back({s[i],i});
    }
    vector<pair<int,int>> xl;
    for (int i=1;i<=n;i++)
    {
        sort(v[i].begin(),v[i].end());
        for (int j=0;j<(v[i].size()/2);j++)
        {
            int l=v[i][j].second;
            int r=v[i][j+(int)(v[i].size()/2)].second;
            if (l>r)
            {
                swap(l,r);
                res++;
            }
            xl.push_back({l+1,r+1});
        }
    }
    for (int i=1;i<=n*2;i++)
    {
        update(i,1);
    }
    sort(xl.begin(),xl.end());
    for (auto x : xl)
    {
        res+=query(x.second-1)- query(x.first);
        update(x.first,-1);
        update(x.second,-1);
    }
    return res;
}

Compilation message (stderr)

shoes.cpp: In function 'long long int count_swaps(std::vector<int>)':
shoes.cpp:27:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   27 |     for (int i=0;i<s.size();i++)
      |                  ~^~~~~~~~~
shoes.cpp:35:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   35 |         for (int j=0;j<(v[i].size()/2);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