merge sort sorting partially - c++

Question

for input 6,2,9,1,5,8 i'm getting 1,2,6,9,5,8.This algorithm is written based on https://gist.github.com/mycodeschool/9678029#file-mergesort_c-c-L28
please help me in getting 1,2,5,6,8,9 as the output also point out the mistake here.Thanks in advance.
#include<iostream>
using namespace std;
void merge(int a[],int l[],int lc,int r[],int rc){
int i,j,k;
i=0;j=0;k=0;
while(i<lc && j<rc){
if(l[i]<r[j]){
a[k++]=l[i++];
}
else{
a[k++]=r[j++];
}
while(i<lc){
a[k++]=l[i++];
}
while(j<rc){
a[k++]=r[j++];
}
}
}
void mergesort(int a[],int n){
int mid;
if (n<2){
return;
}
mid=n/2;
int l[mid],r[n-mid];
for(int i=0;i<mid;i++){
l[i]=a[i];
}
for(int i=mid;i<n;i++){
r[i-mid]=a[i];
}
mergesort(l,mid);
mergesort(r,n-mid);
merge(a,l,mid,r,n-mid);
}
int main(){
int a[]={6,2,9,1,5,8};
int n=6;
mergesort(a,n);
for(int i=0;i<n;i++){
cout<<a[i]<<" ";
}
}

Answer 1

your problem is that is that these loops
while(i<lc){
a[k++]=l[i++];
}
while(j<rc){
a[k++]=r[j++];
}
are inside this loop while(i<lc && j<rc) and they should be outside it as you copy the rest of a[] if b[] is done while a[] has some elements and like wise for b[] and this is the whole merge function
void merge(int a[],int l[],int lc,int r[],int rc)
{
int i,j,k;
i=0;
j=0;
k=0;
while(i<lc && j<rc)
{
if(l[i]<r[j])
{
a[k++]=l[i++];
}
else
{
a[k++]=r[j++];
}
}
while(i<lc)
{
a[k++]=l[i++];
}
while(j<rc)
{
a[k++]=r[j++];
}
}