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Merge two sorted arrays with O(1) extra space


In programming tasks, merging two sorted arrays is a common issue. The merge must be performed with O(1) extra space, which means that no additional memory must be allocated that is proportional to the size of the arrays. This article examines a productive Python solution to this issue.

We must change one of the existing arrays so that it can hold the elements of both arrays in order to merge two sorted arrays with O(1) extra space. To achieve the desired O(1) space complexity, we can use the given arrays as the output merged array.

A well-known algorithmic challenge is merging two sorted arrays with O(1) extra space. We arrive at a space-efficient solution by using the supplied arrays as the output merged array. The Python implementation's steps can be broken down into the following categories:

Initialization of Pointers:

We initialise p1, p2, and p, three pointers. These pointers are used to navigate between arrays and keep track of where each array is right now:

P1 points to the final element of arr1 (i.e., the final element that is valid before adding extra space to arr1).

P2 designates the final component of arr2.

The initial value of p is set to the final element of arr1, which is the last element of the merged array.


In this step, we merge the elements from both arrays into the arr1 in the desired order. The elements in p1 and p2's current positions are compared. The larger of the two elements is copied to position p in arr1 before the corresponding pointer (p1 or p2) and p are decremented.

Implementation of the Optimal Approach



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The provided code defines a Python function called merge_sorted_arrays that merges two sorted arrays into a single sorted array. The merging is done in place, using one of the arrays (arr1) as the destination. The purpose of the code is to demonstrate how to merge two sorted arrays into a single sorted array efficiently, using in-place merging.

Analysis of Time and Space Complexity

The O(1) extra space merging algorithm has an O(n) time complexity, where n is the sum of the elements in both arrays. As was previously mentioned, because we only use a few pointers, the space complexity is O(1).

Benefits of O(1) Additional Space

Over the naive method, the O(1) extra space merging algorithm offers a number of advantages. Because it conserves memory, it is effective in environments with large arrays or limited resources. No matter how large the input array is, the algorithm guarantees constant space usage.

Applications in the Real World

Applications for the O(1) extra space merging algorithm include sorting, searching, and merging operations on devices with limited memory. It is especially helpful in environments with little memory and embedded systems.

With Regard to Other Merging Algorithms

  • Compare the inplace merge and merge sort with the O(1) extra space merging algorithm, as well as other well-liked merging algorithms.
  • Examine each algorithm's time and space complexity to highlight the benefits of the O(1) approach in particular situations.

Treatment of Duplicate Elements

  • Describe how the input arrays' duplicate elements are handled by the O(1) extra space merging algorithm.
  • Describe any changes to the algorithm that are required to guarantee that duplicates are correctly merged and preserved in the final sorted array.

Edge Cases and Unique Situations

  • Determine the edge cases in which the O(1) extra space merging algorithm may have difficulties or behave differently.
  • Offer tactics or additional reasoning to effectively handle edge cases.

The Use of Alternative Languages

  • Provide alternative O(1) extra space merging algorithm implementations in languages other than C++, Java, or JavaScript.
  • Compare the various language implementations of the code and talk about any challenges or improvements that are language-specific.

The Merging Algorithm's Stability

  • Describe the stability concept in sorting and merging algorithms.
  • Examine whether the stability of the input arrays is maintained by the O(1) extra space merging algorithm.

Performance Evaluation

  • Use various input array sizes to performance benchmark the O(1) extra space merging algorithm against other merging strategies.
  • To demonstrate the effectiveness of the algorithm, compare the results.

The Management of Non-Comparable Elements

  • Use conventional comparison operators to handle situations where the elements in the input arrays are not comparable.
  • In order to handle non-comparable elements and still guarantee a sorted merged array, offer fixes or adjustments.

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