The task is to complete merge() function which is used to implement Merge Sort.
First line of the input denotes number of test cases 'T'. First line of the testcase is the size of array and second line consists of array elements separated by space.
Sorted array in increasing order is displayed to the user.
You don't need to take the input or print anything. Your task is to complete the function merge() which takes the array arr, the starting position of the first array (l), the ending position of the first array (m) and the ending position of the second array (r) as its inputs and modifies the array arr such that it is sorted from position l to position r.
Expected Auxiliary Space: O(n)
Expected Time Complexity: O(n) (for the merge() function)
1 <= T <= 50
1 <= N <= 105
1 <= arr[i] <= 103
4 1 3 9 7
10 9 8 7 6 5 4 3 2 1
1 3 4 7 9
1 2 3 4 5 6 7 8 9 10
Testcase 1: The array after performing mergesort is: 1 3 4 7 9.
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