# How does merge sort work

## How does merge sort work step by step?

**Here’s how merge sort uses divide-and-conquer:**

- Divide by finding the number q of the position midway between p and r. …
- Conquer by recursively sorting the subarrays in each of the two subproblems created by the divide step. …
- Combine by merging the two sorted subarrays back into the single sorted subarray array[p..

## What is merge sort and how it works?

Merge sort is one of the most efficient sorting algorithms. It works on the principle of Divide and Conquer. Merge sort repeatedly breaks down a list into several sublists until each sublist consists of a single element and merging those sublists in a manner that results into a sorted list.

## How do you use merge sort?

Algorithm for Merge Sort Step 1: Find the middle index of the array. Step 2: Divide the array from the middle. Step 4: Call merge sort for the second half of the array. Step 5: Merge the two sorted halves into a single sorted array.

## How does merge sort work in C?

In Merge sort, we divide the array recursively in two halves, until each sub-array contains a single element, and then we merge the sub-array in a way that it results into a sorted array. merge() function merges two sorted sub-arrays into one, wherein it assumes that array[l .. n] and arr[n+1 .. r] are sorted.

## Does merge sort need extra space?

Space. Merge sort takes up O ( n ) O(n) O(n) extra space, including O ( l g ( n ) ) O(lg(n)) O(lg(n)) space for the recursive call stack.

## How does merge sort work in Python?

**by splitting the input list into two halves, repeating the process on those halves, and finally merging the two sorted halves together**. The algorithm first moves from top to bottom, dividing the list into smaller and smaller parts until only the separate elements remain.

## How does merge sort recursion work?

**Recursion at work**

- a merge function, which actually combines two lists together and sorts them in the correct order.
- and a mergeSort function, which will continue to split the input array again and again, recursively, and will also call merge again and again, recursively.

## Why merge sort complexity is nLogn?

Mergesort is a divide and conquer algorithm and is O(log n) **because the input is repeatedly halved.**

## Is bottom up merge sort better?

Bottom-up merge sort with linked lists actually requires more extra memory, n lg n + n cells. So, even with linked lists, the top-down variant is the best choice.

## Can merge sort be done without recursion?

**non-recursive**variant of the merge sort, in which the array is sorted by a sequence of passes. During each pass, the array is divided into blocks of size m.

## What is the best case for merge sort?

## Is merge sort the fastest?

Merge sort is more efficient and works faster than quick sort in case of larger array size or datasets. Quick sort is more efficient and works faster than merge sort in case of smaller array size or datasets.

## Can merge sort be done iteratively?

We can also implement merge sort iteratively in a bottom-up manner. We start by sorting all subarrays of 1 element; then merge results into subarrays of 2 elements, then merge results into subarrays of 4 elements. Likewise, perform successive merges until the array is completely sorted.

## What is L and R in merge sort?

**// l is for left index and r is**.

**// right index**of the sub-array. // of arr to be sorted. void mergeSort( int arr[], int l, int r)

## What is an iteration in merge sort?

In Iterative merge sort, we implement merge sort in a bottom-up manner. … Then, we sort all sub-arrays of length 2 by merging length-1 sub-arrays. Then, we sort all sub-arrays of length 4 by merging length-2 sub-arrays. We repeat the above step for sub-arrays of lengths 8, 16, 32, and so on until the whole array is …

## Is merge sort recursive?

**Divide**and Conquer algorithm. It divides the input array into two halves, calls itself for the two halves, and then merges the two sorted halves. … If we take a closer look at the diagram, we can see that the array is recursively divided into two halves till the size becomes 1.

## How does bottom up merge sort work?

**Operation of the bottom-up merge sort algorithm:**

- The bottom-up merge sort algorithm first merges pairs of adjacent arrays of 1 elements.
- Then merges pairs of adjacent arrays of 2 elements.
- And next merges pairs of adjacent arrays of 4 elements.
- And so on…. Until the whole array is merged.

## Is iterative merge sort better than recursive merge sort?

I just implemented the two algorithms and I was surprised when I plotted the results! Recursive implementation is clearly faster than the iterative one. After that, I added the insertion sort combined with both of them and the result was the same.