Merge Without Extra Space.cpp

/*
Given two sorted arrays arr1[] and arr2[] of sizes n and m in non-decreasing order. Merge them in sorted order without using any extra space. Modify arr1 so that it contains the first N elements and modify arr2 so that it contains the last M elements.
 

Example 1:

Input: 
n = 4, arr1[] = [1 3 5 7] 
m = 5, arr2[] = [0 2 6 8 9]
Output: 
arr1[] = [0 1 2 3]
arr2[] = [5 6 7 8 9]
Explanation:
After merging the two 
non-decreasing arrays, we get, 
0 1 2 3 5 6 7 8 9.
Example 2:

Input: 
n = 2, arr1[] = [10, 12] 
m = 3, arr2[] = [5 18 20]
Output: 
arr1[] = [5 10]
arr2[] = [12 18 20]
Explanation:
After merging two sorted arrays 
we get 5 10 12 18 20.


Your Task:
You don't need to read input or print anything. You only need to complete the function merge() that takes arr1, arr2, n and m as input parameters and modifies them in-place so that they look like the sorted merged array when concatenated.
 

Expected Time Complexity:  O((n+m) log(n+m))
Expected Auxilliary Space: O(1)
 

Constraints:
1 <= n, m <= 5*104
0 <= arr1i, arr2i <= 107
*/