898D - Alarm Clock - CodeForces Solution

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n,m,k;
    cin>>n>>m>>k;
    int arr[n],b[n],x = 0;
    for(int i = 0;i<n;i++)
    {
        cin>>arr[i];
    }
    sort(arr,arr+n);
    int count = 0;
    for(int i = 0;i<n;i++)
    {
        b[++x] = arr[i];
        if(x>=k)
        {
            if(b[x]-b[x-k+1]<m)
            {
                count++;
                --x;
            }
        }
    }
    cout<<count<<endl;
    
}