AMR10G.c

#include<stdio.h>
#include<math.h>
#include<string.h>
#include<stdlib.h>
#define gc getchar
#define ll long long int
#define M 1000000007
#define scan(t) t=input()
inline ll input() {
  char c = gc();
  while(c<'0' || c>'9') c = gc();
  ll ret = 0;
  while(c>='0' && c<='9') {
    ret = 10 * ret + c - 48;
    c = gc();
  }
  return ret;
}
void merge(ll * ,ll ,ll ,ll );
void mergesort(ll *a,ll lb,ll ub)
{
    ll mid=(lb+ub)/2;
    if(lb<ub)
    {
        mergesort(a,lb,mid);
        mergesort(a,mid+1,ub);
        merge(a,lb,mid,ub);
    }
}
void merge(ll *a,ll lb,ll mid,ll ub)
{
    ll c[ub-lb+1];
    ll i=0,lp=lb,up=mid+1;
    while(lp<=mid&&up<=ub)
    {
        if(a[lp]<a[up])
        {
            c[i++]=a[lp++];
        }
        else
        {
            c[i++]=a[up++];
        }
    }
    while(lp<=mid)
    c[i++]=a[lp++];
    while(up<=ub)
    c[i++]=a[up++];
    ll j;
    for(j=0;j<i;j++)
    a[j+lb]=c[j];
    return;
}
int main()
{
    ll t,n,k,i,min;
    scanf("%lld",&t);
    while(t--)
    {
        scanf("%lld %lld",&n,&k);
        ll a[n];
        for(i=0;i<n;i++)
        scanf("%lld",&a[i]);
        mergesort(a,0,n-1);
        for(i=0;i<=n-k;i++)
        if(i==0)
        min=a[i+k-1]-a[i];
        else if(a[i+k-1]-a[i]<min)
        min=a[i+k-1]-a[i];
        printf("%lld\n",min);
    }
    return 0;
}