# Merge Sort code not working

I tried coding the merge sort algo after leaning the theory. Can’t understand what’s wrong in my code http://ideone.com/iOpr9P

You should not use sizeof() operator for array parameters.

int sz = sizeof(a)/sizeof(a[0]);

This must not be used if you are passing ‘a’ as parameter array to some function.

‘sz’ will always be 1 in such case.

Have a look at this link - http://www.geeksforgeeks.org/using-sizof-operator-with-array-paratmeters/
for explaination.

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you need to learn a lot .

This code is helpful for u. It is very simple code.

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

#define mx 10

void merge(int arr[], int l, int m, int h)
{
int l1, l2, i;

l1 = l;
l2 = m + 1;
i = l;

int b[h+1];
// int *b = new int [h+l+1]; avabe dile dynamic memory allocation.
while(l1<=m && l2<=h)
{
if(arr[l1]<=arr[l2])
{
b[i++] = arr[l1++];
}

else
{
b[i++] = arr[l2++];
}
}

while(l1<=m)
{
b[i++] = arr[l1++];
}

while(l2<=h)
{
b[i++] = arr[l2++];
}

for(i = l; i<=h; i++)
{
arr[i] = b[i];
}
//delete b;
}

void sortion(int arr[], int low, int high)
{
int mid;

if(low < high)
{
mid = (low + high) / 2;
sortion(arr, low, mid);
sortion(arr, mid+1, high);
merge(arr, low, mid, high);
}

}

int main()
{
int i;
int arr[mx];

for(i=0; i<mx; i++) cin>>arr[i];

sortion(arr,0, mx-1);

for(i=0; i<mx; i++) cout<<arr[i]<<" ";

return 0;
}

the `void mergeSort(int A[],int n)` function only doesn’t have the `left` and `right` parameters, you should add this to your function like this: `void mergeSort(int A[],int left,int right)`

1 Like

made that change @ankitbisla21 . Still same error.Modified code