Mergesort isnt getting submitted

#1

#include<bits/stdc++.h>
using namespace std;
#define ll long long

void merge(ll a[],int l,int r){
ll mid=l+(r-l)/2;

ll i=l;
ll j=mid+1;
ll k=l;
ll temp[1000000000];
while(i<=mid && j<=r){
    if(a[i]>a[j])
    temp[k++]=a[j++];
    
    else
        temp[k++]=a[i++];
    }

if(i<=mid)
temp[k++]=a[i++];

if(j<=r)
temp[k++]=a[j++];
for(int k=l;k<=r;k++)
a[k]=temp[k];
}

void mergesort(ll a[],ll l,ll r){
if(l>=r)
return;

int mid=l+(r-l)/2;
mergesort(a,l,mid);
mergesort(a,mid+1,r);
merge(a,l,r);

}
int main(){
ll n;
cin>>n;
ll a[n];

for(int i=0;i<n;i++)
cin>>a[i];
mergesort(a,0,n-1);
for(int i=0;i<n;i++)
cout<<a[i]<<" ";
return 0;

}

#2

The mistake you have done is , you have used if instead of while in merge function.
I have changed your code and added comments where there was mistakes.Here is the code.