How do I properly implement merge sort - c++

Question

I have the merge sort code below which is not giving proper output.
Input : 1 7 3 9 4 5 2 6 8
Output : 1 5 2 6 7 3 8 1 9.
#include<iostream>
#include<vector>
using namespace std;
void merge(vector<int>& array,vector<int>& helper,int low,int mid,int high)
{
int size = array.size();
for(int i =0;i<size;i++)
helper.push_back(array[i]);
//helper = array; // copy vector elements i .. copying references doesnt work hence
int current = low;
int helperLeft = low;
int helperRight = mid+1;
while(helperLeft<=mid && helperRight <=high)
{
if(helper[helperLeft]<helper[helperRight])
{ array[current] = helper[helperLeft];
helperLeft++;
}
else
{
array[current] = helper[helperRight];
helperRight++;
}
current++;
}
int remaining = mid - helperLeft;
for (int i = 0; i <= remaining; i++)
array[current + i] = helper[helperLeft + i];
// copy the remaining elements from the left only and not right because right elememts are already there in dest (array) sorted.
}
void mergeSort(vector<int>&array,vector<int>& helper,int low,int high)
{
if(low < high)
{
int mid = (low+high)/2;
mergeSort(array,helper,low,mid);// sort left half
mergeSort(array,helper,mid+1,high);// sort right half
merge(array,helper,low,mid,high);
}
}
void mergeSort(vector<int>& array)
{
vector<int> helper;
mergeSort(array,helper,0,array.size());
}
int main()
{
vector<int> v;
int i =1;
v.push_back(i);
v.push_back(i+6);
v.push_back(i+2);
v.push_back(i+8);
v.push_back(i+3);
v.push_back(i+4);
v.push_back(i+1);
v.push_back(i+5);
v.push_back(i+7);
vector<int>::iterator it=v.begin();
while(it!=v.end())
{
cout<<" "<<*it;
it++;
}
cout<<endl;
mergeSort(v);
it = v.begin();
while(it!=v.end())
{
cout<<" "<<*it;
it++;
}
cout<<endl;
}
I am using C++ vectors here instead of arrays as passing size will be a problem?
Can somebody please hep me correct the mistake here?

Answer 1

I got the answer.The correct solution is posted below.
#include<iostream>
#include<vector>
using namespace std;
void merge(vector<int> &array,int low,int mid,int high)
{
vector<int> helper(array);
//helper = array; // copy vector elements i .. copying references doesnt work hence
int current = low;
int helperLeft = low;
int helperRight = mid+1;
while(helperLeft<=mid && helperRight <=high)
{
if(helper[helperLeft]<helper[helperRight])
{
array[current] = helper[helperLeft];
helperLeft++;
}
else
{
array[current] = helper[helperRight];
helperRight++;
}
current++;
}
while(helperLeft<=mid)
array[current++] = helper[helperLeft++];
// copy the remaining elements from the left only and not right because right elememts are already there in dest (array) sorted.
}
void mergeSort(vector<int>&array,int low,int high)
{
if(low < high)
{
int mid = (low+high)/2;
mergeSort(array,low,mid);// sort left half
mergeSort(array,mid+1,high);// sort right half
merge(array,low,mid,high);
}
}
void mergeSort(vector<int>& array)
{
mergeSort(array,0,array.size()-1);
}
int main()
{
vector<int> v;
int i =1;
v.push_back(i);
v.push_back(i+6);
v.push_back(i+2);
v.push_back(i+8);
v.push_back(i+3);
v.push_back(i+4);
v.push_back(i+1);
v.push_back(i+5);
v.push_back(i+7);
vector<int>::iterator it=v.begin();
while(it!=v.end())
{
cout<<" "<<*it;
it++;
}
cout<<endl;
mergeSort(v);
it = v.begin();
while(it!=v.end())
{
cout<<" "<<*it;
it++;
}
cout<<endl;
}