In-Place Merge Sort | Set 2

Given an arrayA[] of size N, the task is to sort the array in increasing order using In-Place Merge Sort.

Examples:

Input: A = {5, 6, 3, 2, 1, 6, 7}
Output: {1, 2, 3, 5, 6, 6, 7}

Input: A = {2, 3, 4, 1}
Output: {1, 2, 3, 4}

Approach: The idea is to use the inplace_merge() function to merge the sorted arrays in O(1) space. Follow the steps below to solve the problem:

• Create a recursive functionmergeSort() that accepts the start and the end indices of the array as parameters. Now, perform the following steps:
  • If size of the array is equal to 1, simply return out of the function.
  • Otherwise, calculate the middle index to split the array into two subarrays.
  • Recursively call mergeSort() on the left and right subarrays to sort them separately.
  • Then, call the inplace_merge() function to merge the two subarrays.
• After completing the above steps, print the sorted arrayA[].

Below is the implementation of the above approach:

1 2 3 5 6 6 7

Time Complexity: O(N * log(N))
Auxiliary Space: O(1)

Alternate Approaches: Refer to the previous article for other approaches to solve this problem.