Merge sort python stackoverflow. The solution is to pass the partial array location to the child process so the child knows which part of the full array to update. When you say a[:mid], python creates a 'copy' ( let's not worry about the exact type of copy ) of the original. Mar 31, 2021 · Hi I am attempting to make a Merge Sort algorithm for fun, and do not want to just copy code off the internet. Every two adjacent blocks are merged (as in normal merge sort), and the next pass is made with a twice larger value of m. Merge sort is a prime example of the divide-and-conquer approach and is utilized to sort large data sets. . I will sink into the I'm trying to learn how to do a merge sort. There are some other issues or unneeded code. pyplot as plt import math from collections import deque May 11, 2014 · How should I find number of swaps done in a merge sort , here is the algorithm. I completed the basic version, which is only referred by the array, and am now working on the index version. What is the problem here with my code? I am trying to implement it without referring any resources and unnecessarily writing this line since some d May 21, 2015 · The purpose its to write it on python, so far I have coded all of it but it does not run properly, everytime I run it prints: function merge at 0x0000000002024730. Essentially I began by trying to isolate the minimum elements in each list and then I compared the Feb 11, 2019 · I am currently practicing or my interview and was doing the merge-sort for the linked list problem. even insertion sort can do this, you can use binary insert as well. Apr 22, 2016 · You are forgetting the terminating case of your merge_sort function, which returns 1. I have implemented Selection Sort, Insertion Sort and Bubble Sort. I haven't bothered porting it to Python because Python is so slow, and due to Python being an interpretive language, 4 way merge sort would probably be slower in Python than 2 way (with a compiled language, 4 way is about 15% faster than 2 way). Enable to get the total split inversion in the list you must add the left half, right half and merge split inversions. count=0 def mergesort (elist,co Oct 7, 2019 · You're confused about how classes and methods work. Mar 23, 2013 · I am practicing merge sort and am curious if my second version is better than the first -- it seems to be in terms of memory requirement since I am popping from a list instead of just moving indices Feb 2, 2024 · Use Iterative Merge Sort in Python Merge sort is a popular sorting algorithm utilized to sort the elements of any given data structure. Aug 11, 2020 · With the bubble, you're only dealing with a single array. Currently, I have a 2d array with a Unix timecode(fig 1) and merge sorting using (fig 2) I am trying to check the first value in each array Apr 3, 2010 · How to convert a normal merge sort into an in-place merge sort (or a merge sort with constant extra space overhead)? All I can find (on the net) is pages saying "it is too complex" or "out of scope of this text". I tried to do this without using left and right parameters which are found elsewhere, only using slices. and forget about python for a second, how can you merge two non-monotonically increasing sorted list. Now I want to implement my insertion sort and merge sort into a Tim sort. So here is my practice of a merge sort, I looked at other questions however they were many more lines com Feb 7, 2016 · Sort-Merge-Join Algorithm in Python Asked 9 years, 2 months ago Modified 9 years, 2 months ago Viewed 2k times python pandas sort columns after merge Asked 7 years, 8 months ago Modified 7 years, 8 months ago Viewed 6k times Oct 22, 2015 · I'm trying to use a merge sort algorithm to count the inversions in an array that contains all the numbers in the range 1 to 100,000. I want to use turtle module. You can look at merge sort to understand this better. It's working nicely on a list of integers but I thought a more practical application is need. I want to create a function merge that gets these lists as parameters and returns a new sorted list L Jul 9, 2021 · In in_place_merge_sort, I don't see any code to handle the case where there is a single run remaining and nothing to merge at the end of a pass, the case where middle >= last. Wait wait, I promise I have more than Zoolander references to offer. Jan 13, 2022 · Also try to provide sample output of what you're trying to achieve. I want it to work both in ascending (reverse = False) and descending ( Aug 30, 2017 · Similar to the optimized top down merge sort, copying is avoided by changing the direction of merge based on the merge pass. The idea is simple; as long as the value T (threshold) is exceeded, merge sort should run recursively, whereas when the value is less than or equal to T, bubble sort is called. May 28, 2015 · I'm trying to learn Python and am working on making an external merge sort using an input file with ints. Which is why I have not referred to another person's Stack Overflow thread. The issue I've discovered was the problem within my partition method. I think it's a great example of w Jul 1, 2020 · I wrote a short Merge sort algorithm in Python 3. Jul 23, 2025 · The provided Python code implements the Merge Sort algorithm, a divide-and-conquer sorting technique. Each tuple in the I have already made code for insertion sort and merge sort. Whenever I partition and request the first half, the other half t Feb 4, 2018 · You'll need to complete a few actions and gain 15 reputation points before being able to upvote. import random as r import heapq as h def ksort(l): a = [0]*len(l) c = [] while True: for i in range(len(a)): if a[i] >= (len(l[i])): a[i] = -1 j = 0 #check if done for i in range(len(a)): if a[i] == -1 Mar 17, 2016 · I'm trying to merge two sorted arrays into a sorted array. Sep 6, 2023 · So, I was tasked to create a hybrid sort function in python that would utilize bubble and merge sorts. Here is Feb 25, 2012 · I am trying to write merge sort and stuck here. The data to be sorted contains numbers which so I decided to implement merge sort in Python3 to handle large CSV files (working with 5GB files >. Here is the python code: #Recursive Merge Sort import math ent = [10000, 967, 87, 91, 117, 819, 403, 597, 1201, 12090] def merge(L1, L2): while len(L1) and len(L2) != 0: L. I just got it somewhere in the net. sometimes Sep 18, 2023 · Im trying to implement a natural merge sort in python, I have my get_sorted_run_length working correctly, but my natural_merge_sort is sorting the most of list correctly but for some reason, is not sorting the last two ints in the list. It works like this mergeSort (list_here) May 14, 2021 · I have created a program where numbers are generated randomly for a list/ array. Below is the merge sort I am implementing. Sep 1, 2022 · At that point, those sub-arrays are merged to create a sorted run of size 2. Thus, left and rigt are int when the recursion reaches the bottom, and you need to take account for that in your code. To draw a single bar i use the function draw_bar, and to draw the entire array there is the function draw_bars. And in mergesort function, you're returning nothing. The file will look something like this Jun 12, 2017 · Merge Sorting without the Overflow Recursion, so hot right now. With the merge sort, you're dealing with recursion and several layers of arrays. I am trying to sort this list of tuples after the number on the second index using the merge sort algorithm, but I am very unsure on how to do so. up( I understand how merge sort work but however when I try to implement in python, I think I am still a little confused about how things are really working out on stack. This is the multidimensional array I am try I started learning python a few days back and I was trying to solve sorting algorithms. from heapq import merge. arr is supposed to be the total list, so you should only replace a part of it: arr[l:h+1] = merge(arr,l,mid,h) Aug 18, 2011 · This is one advantage insertion-sort,selection-sort and quick-sort have over merge-sort (when implemented as above) Speaking of which, something like quick-sort is both naturally-elegant code, naturally efficient-code, and doesn't waste any memory (google it on wikipedia- they have a javascript implementation from which to base your code). It was invented by Tim Peters in 2002 for use in the Python programming language. A typical merge sort program in python (as far as I know) inclu Nov 18, 2013 · here is a merge sort logic in python : (this is the first part, ignore the function merge()) The point in question is converting the recursive logic to a while loop. Let’s break down how it works in Python, with clear examples and practical applications. I can Jun 11, 2018 · I'm trying to implement merge sort in Python that sorts either in ascending or in descending order depending on the parameter you give it. Jun 28, 2011 · basically I have a bunch of files containing domains. I tried making an adjustment to compensate for Pythons zero-based indexing but this did Sep 7, 2017 · I was trying to complete a merge sort in Python. This is a multiple pass solution. I'm using heapq. It works fine when I input a small data set but doesn't return Jul 20, 2020 · So I understand how to make the merge sort algorithm in Python 3, and this is my code below for implementing the function: def x(arr): for i in mergeSort(arr): yield from i def mergeSo Feb 10, 2021 · The code is not checking for a terminating condition, when all elements have been merged. Then the sort follows the call chain up and down, depth first, left first, merging runs of ever increasing size, until it gets to the initial call where two sorted runs are merged back into the original array. In every pass, partition the list into non-overlapping chunks of size whatever. What's reputation and how do I get it? Instead, you can save this post to reference later. (Initially, m = 1). The number of merge passes is determined in advance based on n, and if it would be an odd number of passes, the first pass can swap pairs of elements in place, leaving an even number of merge passes to do so the sorted Jul 19, 2016 · I was reading about merge sort(In place) in my algorithm book (Intro to algorithms 3rd edition Cormen), and I decided to implement it in Python. By the way, which python version you are using? Also, can you provide the complete stack trace? Feb 19, 2021 · Im trying to implement merge sort in Python based on the following pseudo code. I have checked merge function. Sep 1, 2021 · There was an almost-exactly similar question asked a few days ago on this site. The code works very well and sorts the numbers. Apr 3, 2012 · I have implemented a naive merge sorting algorithm in Python. Aside from that, I want to be able to print out each step of the sorting algorithm. Start with a chunk size of 2 and double the chunk size in every pass. My best time at the moment is 105 seconds and I can't think of a way to make thi Oct 17, 2023 · 0 If you want a production quality merge and sort algorithm, you can always check the implementation of heapq. As the documentation says, it is very similar to using itertools (but with more limitations); if you cannot live with those limitations (or if you do not use Python 2. Apr 11, 2023 · You'll need to complete a few actions and gain 15 reputation points before being able to upvote. I've sorted each individual file based on its TLD using . When I run this code though, the output is wrong. Upvoting indicates when questions and answers are useful. <) and I think I have the logic down correctly, the problem is, that it's quite slow, I'm just Nov 26, 2018 · I tried to write a merge sort with multiprocessing solution from heapq import merge from multiprocessing import Process def merge_sort1(m): if len(m) < 2: return m middle = le Aug 26, 2014 · I've been having trouble using merge sort on a linked list. I would like to combine the two lists into one sorted list. The count computation was done , the problem is : the count variable is not returned. merge(lst1, lst2) This is very efficient as merge expects lst1 and lst2 to already be sorted, so it only looks at the first element as it goes. Here is my code import turtle from random import randint import time def draw_bar(x,y,w,h): turtle. This solution finds the left and right partitions using Python's handy // operator, and then passes the left, right, and array references to the merge function, which in turn rebuilds the original array in place. This is the list of tuples I am trying to sort: Jul 4, 2021 · I'm trying to create an algorithm to merge two ordered lists into a larger ordered list in Python. You mention you want to sort but your function is called merge. import sys sequence = [6, 5, 4, 3, 2, 1] def merge_sort(A, first, last): if first < last: middle = Nov 28, 2022 · i want to sort the array in descending order using mergeSort this is the code for my MergeSort implementation in ascending order def MergeSort(B): if len(B) <= 1: return Jan 1, 2021 · I want to make a mergesort visualizer in python. I have a function called May 18, 2013 · 1 The algorithm you implemented is (a flawed) quick sort without removing the so-called "pivot" element, in your case m. I got it working with 2 separate functions but I can't get I am trying to make merge sort using two functions in python. Jun 1, 2021 · I am trying to sort this multidimensional array after the number on the first index using the merge sort algorithm, but I am very unsure on how to do so. In this tutorial, we will explore how to implement merge sort in Python, a powerful sorting algorithm that uses a divide-and-conquer approach. The arrays are merging fine. my code works fine with my small input file (10 elements) but when it goes to 100000, it seems return incorrect answer from brute search. 1. However, it's true that in practical applications, a hybrid mergesort-insertionsort algorithm is usually faster than merge sort. But let’s face it — recursion is a popular topic Apr 18, 2016 · I have implemented the mergesort algorithm using a post on codereview. Split every chunk into 2 and call merge on the 2 parts It doesn't look like that you posted the complete code. For that i've created three method. Is the best way just to do a sort or is there a smarter way to do this in Python? python list sorting edited Apr 7, 2012 at 8:12 community wiki 2 revs Bjorn Tipling | 22 Answers Sorted by: 135 Jun 30, 2019 · The code is incorrect: the is some confusion about index values and slice boundaries, and other mistakes too: array indices start at 0 in python, so you should call Merge_sort(ar, 0, n) the slice length n1 is off by one, it should be n1 = q - p the test for recursion should compute the slice length and only recurse for slices with at least 2 elements. merge(lst1, lst2, lst3, lst4) At this point, merged is actually itself an iterator. So unless I need to write a merge_sort and a corresponding merge_two_halves function which sorts the parameter list of tuples. Aug 12, 2017 · Nothing says that merge sort must divide the list at the center. The merge operation you do does not need to do any merging as in merge sort, because the a call to mergeSort(left) would already return a sorted left, if you were to handle the pivot correctly. Here's a 2-pass algorithm that demonstrates it: First, iterate the file in 50k line chunks, sort the lines in a chunk and then write this sorted chunk into a file. May 22, 2016 · Additionally, the fact that the merge function modifies a in place makes it extremely difficult to ascertain what is happening. During each pass, the array is divided into blocks of size m. This tutorial discusses the merge sort algorithm and how to implement it in Python. Aug 30, 2021 · I am trying to count the number of inversions inside a Merge Sort algorithm. I know there are many implementations out there, but I have not been able to find one that followis this pattern with Sep 29, 2013 · I see some answers that mention pivots but I would recommend not associating the word "pivot" with merge sort because that's an easy way to confuse merge sort with quicksort (which is heavily reliant on choosing a "pivot"). May 6, 2014 · Here is the code for merge sort. It is throwing an error "RuntimeError: maximum recursion depth exceeded". sort() both accomplish what you need. sort(kind='mergesort') I am afraid you can't do better than this, unless you write your own sorting function as a python extension, à la cython. Please let me know if I am missing the Merge Sort Using Python Asked 9 years, 5 months ago Modified 9 years, 5 months ago Viewed 174 times Dec 1, 2019 · Here is the code for the function which must return new sorted list, how do I get only the final arr printed, since it prints all steps? def mergeSort(list_to_sort, ascend=True): arr=list_to_s Oct 21, 2017 · To sort a list of list and specify it to merge based on the middle number of each sublist? Is there a trick with python that will allow this to work? Only thing I have been able to find about this is using the built-in sorting function, which I do not want to do. Code courtesy: Rosettacode Merg Jan 4, 2022 · As merge returns the result for a sub list, you should not assign it to arr. Mar 9, 2019 · Recursive merge sort splits problem unless list of unsorted values reduces to a list of singletons - single elements that can be compared. But recursion makes a lot more calls on the stack which in turn makes it less memory efficient. But I got an error like IndexError: list assignment index out of range whenever run my code. Given a linked list (has next and val attributes), 4-2-1-3, I am supposed to sort it to be 1-2-3 Jul 4, 2022 · Merge nums1 and nums2 into a single array sorted in non-decreasing order. merge_sorted_list has been ignored. Nov 16, 2012 · python sorting text merge mergesort edited Nov 16, 2012 at 20:30 MostafaR 3,70511924 asked Nov 16, 2012 at 19:55 kylin 32 2 Jun 8, 2019 · I'm trying to implement the python code for Merge Sort Algorithm using recursive functions in python. Jan 1, 2021 · I have to create a code that let visualize how the merge sort works, using turtle module. But if we go larger data that has to be sorted, something goes wrong. The compiler is correct (by definition ): there is no function _merge_sort. In your merge function, in else block, you're returning whats being returned by mergesort function. After the sublists reaching a certain Jan 13, 2015 · You can use from numpy import concatenate, sort c = concatenate((a,b)) c. It breaks down an array into smaller subarrays, sorts them individually, and then merges them back together to create a sorted array. The reallocation happens here and the size is calculated as: new_allocated = (size_t Sep 20, 2012 · if len(L) < 2: Wikipedia actually has a nice animation that shows how Merge sort works: Basically, merge() combines two sorted lists and returns a single sorted list. That's what atomize() does: given a list, produces a list of lists-singletons (order O(n)). But the Jan 25, 2023 · 2 Is there ever a situation where you should use a recursive merge sort over an iterative merge sort? Originally I thought that iterative approaches to merge sort were typically faster although I could not prove that in my own implementations. the merge loop is incorrect: you should Dec 30, 2017 · when I implement a merge sort in python, I doubt that the auxiliary space complexity is O (logn) which is documented is most analysis (account for the call stack in recursion) if I implement in Python based on the following scripts. But honestly, I can't follow the flow of the code I mean, I can't get how it is implemented. Merge sort typically divides the array in half, because that's a whole lot easier to write, but it doesn't have to be that way. I don't Jan 21, 2021 · it has been several days of trying to implement a functional recursive merge sort in Python. _data. When you put too much extra stuff in the list it eventually needs to be reallocated which potentially slows down the program (see this part of the source code). Note that merge also allow multiple (already sorted) arguments: merged = heapq. if you're sorting data on-disk (merge 2 files), IO times will likely dominate and python's speed won't matter much, just the number of operations you do (and hence the algorithm). sort() recursively breaks up your list into pairs and sorts the pairs one step at a time, merging two sorted pairs to form a larger sorted list at every step in the recursion. rand(10, 5)) I add more column (s) by assignment: df['mean'] = df. They are correctly visualizing th Jul 19, 2019 · When you instantiate a list Python will allocate the memory necessary for holding the items plus some extra memory for future appends / extends. Jul 5, 2018 · I am working on merge sort in Python. To Sep 15, 2020 · The mergeSort function without the recursion does not sort the array, it just merge (hence the name) the two half that are supposed to be already sorted. The benchmarks and comments there are insightful as well. Also, minor nomenclature note: You're working with list s (specific return type) or sequences (generalizing to many different input types), not "arrays". You are correct that you should cache the slice in a variable to avoid doing it multiple times. I modified the questions code and it seems to be working. Oct 28, 2024 · Merge sort stands out among sorting algorithms for its reliability and predictable performance. Apr 25, 2025 · In this blog, we will explore the merge sort algorithm in the context of Python, covering its basic concepts, how to implement it, common and best practices. Sep 30, 2022 · I'm trying to solve merge sorted linked list problem. But it gets into infinite loop. I assume you are doing this to learn merge sort or LIFO, but if not, since your stack is just a python list (array), the functions sorted(s. set it as first column leaving the order of the other columns untouched? I am having issues regarding my merge_sort function, specifically performing recursive sorting the right sub-list. In second pass, open all these files and merge to the output file. Here's the updated code Mar 23, 2016 · Merge two files in Python and sort Asked 9 years, 3 months ago Modified 9 years, 3 months ago Viewed 4k times Oct 13, 2009 · Bottom-up merge sort is a non-recursive variant of the merge sort, in which the array is sorted by a sequence of passes. This is why you need to call the function on each half of the array before merging the two. Algorithm and test code is below: import time import random import matplotlib. Is there any way to Oct 21, 2015 · Another option would be to use bottom up merge sort, which skips the recursion steps and just starts merging even runs with odd runs, with an initial run size of 1. Jun 6, 2014 · For a merge sorting to work the elements you are merging should be already sorted in respect to the other elements of their list. Note that top down merge sort is mostly academic. DataFrame(np. Recursion. Feb 5, 2013 · I have here a code for sorting lists using merge sort. Jun 21, 2018 · Just to be clear, this is for a class, right? Just making sure you're not reimplementing this for real code (where the One True Python sort of list. I've never programmed in Python before, so I used several resources with commands that seemed foreign to me, to gain a better Mar 12, 2025 · Why does this code fail to sort the random array? I've tried fiddling with the indexes a bit but to no avail. I can see that the example of Tim sort uses start, mid and end May 1, 2020 · Firstly, don't use list as identifier. Jun 20, 2020 · Merge sort in python issue [closed] Asked 4 years, 8 months ago Modified 4 years, 6 months ago Viewed 83 times Oct 7, 2019 · I'm very new to programming and Python, and I try to understand the merge sort. sort(key=func_that_returns_tld) now that I've done that I want to merge all the files Jun 18, 2020 · I am trying to implement the merge-sort algorithm in Python 3. merge, which ships with Python. I have a question about the Python version of recursive Merge Sort. addlast , print and merge For linked list class created a three objects obj and obj1 (To create two linked l Feb 18, 2014 · Below is intended for a merge sort written in Python. The hint that was given for this assignment was: # if min_ < max_ # calculate Sep 24, 2014 · * Merge the sorted [3] and [6] halves (if you're using the graphical visualizer, this happens at step 31; if using the debugger, put a breakpoint at line 12 and this will be the first time the breakpoint is hit): Nov 17, 2018 · I'm stuck again on trying to make this merge sort work. Even if you have an amazing mind that can keep track of all that action, save that brain energy for tackling the problem rather than flow control! Apr 9, 2024 · I'm a beginner Python learner and trying to implement Sorting Algorithm Visualizer as a project. random. Jan 21, 2009 · Each list is already sorted by a property of the object that is of the datetime type. In this list, I need to calculate how long it will take to sort the list and also the number of swaps it will take t Nov 25, 2016 · I'm trying to implement a mergesort with Python multiprocessing without any built-in functions so that each level of the sort gets launched in a new process. You have gone to a lot of trouble to set up this class, but then you've ignored those encapsulation protections when you try to recur on the halves of your list: left = _merge_sort(lst[:mid I need to write a mergeSort function that will merge two files, and sort the lists contained in the files in alphabetical order based on a word in the list. I found when I use middle = (len (x)-1)//2, the right part was in infinity loop and never reached the base case, but if I changed m iddle = len (x)//2, it worked normally. Apr 20, 2022 · How do I Add counter to count the number of primitive operations in python for this program? And how do I plot the worst case, best case, and average case for time complexity? def mergeSort(ar_list Dec 20, 2015 · This is called merger. from math import floor Feb 17, 2011 · I've implemented what I believe to be a merge sort algorithm in python. I recently started with merge sort algorithm. Apr 1, 2025 · In this blog, we will explore the implementation of merge sort in Python, covering the fundamental concepts, usage methods, common practices, and best practices. So I downloaded a text file with Aug 3, 2021 · I'm having trouble understanding how the recursive merge sort algorithm works, I understand how it theoretically works : if there's more than one element in an array find its middle and divide the I'm implementing a merge sort with inversion count. I'm trying to implement a merge sort function. Mar 8, 2012 · I implemented merge-sort in python import sys def mergeSort (array): if len (array) < 2: return array middle = len (array) / 2 left = mergeSort (array [:middle]) right = Oct 14, 2020 · I need to optimize my sort (a merge sort), so that with a list of size 10^6 will be sorted in less than 100 seconds. merge. The problem is that I can't find what I am doing wro Dec 31, 2017 · How can I count the swaps in a Merge Sort Algorithm in Python [duplicate] Asked 7 years, 6 months ago Modified 7 years, 6 months ago Viewed 3k times Nov 10, 2021 · Here is a simple merge sort algorithm I tried to implement in python. How can I implement the Merge Sort algorithm with 4-way Jul 5, 2020 · Suppose we have two lists L1 and L2 that contain integers which are sorted in ascending order. May 20, 2020 · You're right that slicing is O (n), but extending once is almost surely faster than appending multiple times because multiple calls to append may require multiple memory reallocations, which is costly compared to the (presumably) single allocation used by extend. The merge sort algorithm follows the divide - and - conquer paradigm. So if you want to merge 3 lists those lists should be sorted before trying to merge them. Here's the function that implements the merge part of the algorithm: Apr 15, 2012 · I am new to python and am trying to implement merge_sort in Python, here is my code. For reference I am learning from tutorialspoint. So, you don't need to change the merge function. Feb 1, 2017 · I'm very new to python, however not new to programming as I've been doing C for some time. Also, due to recursion in merge function, you're ending up setting variables lista and listb to returned values of merge function which might be none since mergesort isn't returning anything (thus None Jun 8, 2018 · So I have a function defined that works great at doing merge sort on a linear array if it is implemented by its lonesome, but if I put it into a class it bugs out. _data) or s. I know how to do that in general (so the question itself isn't about merging lists), but for learning purposes I want to write it with a l Dec 10, 2013 · So when you call mergesort(a[:mid]) for example, what you get back is a new sorted version of those elements, while the original a[:mid] stays exactly the same. See this question for a similar problem, but keeping only the unique values in the merged array. It's quite possible to write a merge sort that divides the list in thirds, or divides the list at len/4, or however else you decide to do it. Jan 26, 2016 · Not sure where I am going wrong with my implementation of merge sort in python. Mar 5, 2021 · Link to java example of a 4 way top down hybrid merge sort + insertion sort (for small runs). you sorting and merging There are numerous implementations of merge sort I've seen, however, I'm trying to write one which translates literally from the algorithmic definition of merge sort: Split the arrays till you've 1 Oct 31, 2012 · I have the following DataFrame (df): import numpy as np import pandas as pd df = pd. But in the mergeSort Function an error is coming :--- RuntimeError Apr 2, 2015 · Just for reference, you can simplify your logic somehwat, both in terms of using python slicing and slightly changing the logic of merge: def sort(number_list): Sep 5, 2022 · I found the following code from geeks for geeks and I don't seem to understand how the sub-arrays are being sorted(i. May 4, 2014 · However, each partial file must be sorted before you write them to the disk. That name applies to a method, and must be called with a Sorter object. But the code is not working as expected. Updating the main array is a challenge since each layer of recursion only sees part of the full array. append(L1[0]) Aug 30, 2017 · You could also use the heapq module's merge function, which takes advantage of the fact that each nested list is already sorted, rather than simply sorting the flattened list. mean(1) How can I move the column mean to the front, i. I see no line where the return of the function merge() is assigned to some variable (like A = merge(A)). I have trouble understanding how it manages to achieve the correct result, as when I try to trace its logical steps I end up with an out of order l Jun 1, 2021 · I think the trick is you should change the array A inside the function merge() instead of making the new array and return it. The value of q in the code is not decreasing as expect Jun 8, 2012 · Timsort is a hybrid sorting algorithm, derived from merge sort and insertion sort, designed to perform well on many kinds of real-world data. The code is import random Listy = [] for x in range( Jun 11, 2018 · class MergeSort (object): ''' Instantiates an array into the object from which the method 'merge_sort' can be called. The list should be sorted in reverse order (biggest-smallest). The answer given was that your conclusion is correct: if you're only counting the number of key comparisons, merge sort is always better than insertion sort, even on small lists. 6) you can do something like this: Since, in your code merge returns a pair, mergesort must also return a pair. EDIT: The issue here is the way python list slicing works. Can anyone point out why? Thanks def merge_sort(a): '''implement merge sort Dec 29, 2014 · Python merge sort Asked 10 years, 1 month ago Modified 10 years, 1 month ago Viewed 172 times You will need a merge function (the same or almost same merge function) which will be called repeatedly. I have not made many modifications except adding a counter for the condition to flip the values if the value on the righ Oct 13, 2013 · Python standard library offers a method for it: heapq. The function should not return the final sorted array, but instead, be stored inside the array nums1. We’ll learn how it works and how to implement it in Python and discuss its real-world applications. sort and the built-in that wraps it, sorted, are the only sorts you should be using). Jan 21, 2009 · Eg. At line 3 there is 'arr' which I don't see is defined anywhere. when we sort the left sub-array and then the right sub-array and then, merge Jan 13, 2022 · So I'm trying my best to visualize how this merge sort process would go, but I'm stuck with the recursions and triple While loops, and how do these recursions affect the current divisions of the array [1,9,7,10,11] the first half and [8,3,2,5,6,4] the second half. merge, and my code almost works, but it seems to be sorting my lines as str Here's another answer: use the "merge" function of heapq: import heapq merged = heapq. e. siwlf hbt ogckmd hio jotjf bnd kzxlou kuhqfbe fjris ofdttac