#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>
#include<iostream>
#include<vector>
#include<cassert>
#include<sstream>
#include<map>
#include<set>
#include<stack>
#include<queue>
#include<algorithm>
using namespace std;
#define pb push_back
#define mp make_pair
#define clr(x) x.clear()
#define sz(x) ((int)(x).size())
#define F first
#define S second
#define REP(i,a,b) for(i=a;i<b;i++)
#define rep(i,b) for(i=0;i<b;i++)
#define rep1(i,b) for(i=1;i<=b;i++)
#define pdn(n) printf("%d\n",n)
#define sl(n) scanf("%lld",&n)
#define sd(n) scanf("%d",&n)
#define pn printf("\n")
typedef pair<int,int> PII;
typedef vector<PII> VPII;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef long long LL;
int main()
{
    vector < long long  int > arr;
    long long int n,i,ans=1000000000000000000LL,k;
    sl(n),sl(k);
    arr.resize(n);
    for(i=0; i<n; i++)
        sl(arr[i]);
    sort(arr.begin(),arr.end());
    for(i=0; i<=n-k; i++)
        if( (arr[i+k-1]-arr[i]) < ans)ans=arr[i+k-1]-arr[i];
    cout << ans << endl;
    return 0;
}

• Problem Description
  Given a list of N integers, your task is to select K integers from the list such that its unfairness is minimized.
  
  if (x1,x2,x3,…,xk) are K numbers selected from the list N, the unfairness is defined as 
  
  max(x1,x2,..,xk)-min(x1,x2,….,xk)
  
  where max denotes the largest integer among the elements of K, and min denotes the smallest integer among the elements of K .
  
  Input Format 
  
  The first line contains an integer N. 
  The second line contains an integer K. 
  N lines follow. Each line contains an integer that belongs to the list N.
  
  Note: Integers in the N list may not be unique.
  
  Output Format 
  An integer that denotes the minimum possible value of unfairness.
  
  Constraints 
  2<=N<=10^5 
  2<=K<=N 
  0<=integer in N<=10^9
• Test Case 1
  Input (stdin)7
  3
  10
  100
  300
  200
  1000
  20
  30
  Expected Output20
• Test Case 2
  Input (stdin)10
  4
  1
  2
  3
  4
  10
  20
  30
  40
  100
  200
  Expected Output3