C++ Program to Implement Merge Sort

Code:

#include   iostream

using namespace std;

// A function to merge the two half into a sorted data.
void Merge(int *a, int low, int high, int mid)
{
// We have low to mid and mid+1 to high already sorted.
int i, j, k, temp[high-low+1];
i = low;
k = 0;
j = mid + 1;

// Merge the two parts into temp[].
while (i <= mid && j <= high)
{
if (a[i] < a[j])
{
temp[k] = a[i];
k++;
i++;
}
else
{
temp[k] = a[j];
k++;
j++;
}
}

// Insert all the remaining values from i to mid into temp[].
while (i <= mid)
{
temp[k] = a[i];
k++;
i++;
}

// Insert all the remaining values from j to high into temp[].
while (j <= high)
{
temp[k] = a[j];
k++;
j++;
}


// Assign sorted data stored in temp[] to a[].
for (i = low; i <= high; i++)
{
a[i] = temp[i-low];
}
}

// A function to split array into two parts.
void MergeSort(int *a, int low, int high)
{
int mid;
if (low < high)
{
mid=(low+high)/2;
// Split the data into two half.
MergeSort(a, low, mid);
MergeSort(a, mid+1, high);

// Merge them to get sorted output.
Merge(a, low, high, mid);
}
}

int main()
{
int n, i;
cout<<"\nEnter the number of data element to be sorted: ";
cin>>n;

int arr[n];
for(i = 0; i < n; i++)
{
cout<<"Enter element "<
cin>>arr[i];
}

MergeSort(arr, 0, n-1);

// Printing the sorted data.
cout<<"\nSorted Data ";
for (i = 0; i < n; i++)
        cout<<"->"<

return 0;
}


Output:

Case 1:

Enter the number of data element to be sorted: 10
Enter element 1: 23
Enter element 2: 987
Enter element 3: 45
Enter element 4: 65
Enter element 5: 32
Enter element 6: 9
Enter element 7: 475
Enter element 8: 1
Enter element 9: 17
Enter element 10: 3

Sorted Data ->1->3->9->17->23->32->45->65->475->987



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