Python - Reverse sort Matrix Row by Kth Column
Last Updated :
03 May, 2023
Sometimes, while working with data, we can have a problem in which we need to perform sorting of each row of records by some of decisive factor like score. This kind of problem is common in competitive programming and web development. Lets discuss certain ways in which this task can be performed.
Method #1 : Using sorted() + lambda + reverse The combination of above methods can be used to perform this task. In this, we sort the list in descending order using reverse by particular column using lambda function and list comprehension.
Python3
# Python3 code to demonstrate
# Reverse sort Matrix Row by Kth Column
# using sorted() + lambda + reverse()
# Initializing list
test_list = [['Manjeet', 65], ['Akshat', 42], ['Akash', 38], ['Nikhil', 192]]
# printing original lists
print("The original list is : " + str(test_list))
# Initializing K
K = 1
# Reverse sort Matrix Row by Kth Column
# using sorted() + lambda + reverse()
res = sorted(test_list, key = lambda ele: ele[K], reverse = True)
# printing result
print ("List after performing sorting of matrix records : " + str(res))
Output :
The original list is : [['Manjeet', 65], ['Akshat', 42], ['Akash', 38], ['Nikhil', 192]] List after performing sorting of matrix records : [['Nikhil', 192], ['Manjeet', 65], ['Akshat', 42], ['Akash', 38]]
Time complexity: O(mlogn+nlogn), because it performs the same number of iterations as the original code.
Auxiliary space: O(m*n) as well, because it creates a dictionary with m * n keys and a list of m * n elements
Method #2 : Using sort() + itemgetter() The combination of above methods can also be used to solve this problem. In this, we perform the task of lambda function using itemgetter and sort() performs sorting.
Python3
# Python3 code to demonstrate
# Reverse sort Matrix Row by Kth Column
# using sort() + itemgetter()
from operator import itemgetter
# Initializing list
test_list = [['Manjeet', 65], ['Akshat', 42], ['Akash', 38], ['Nikhil', 192]]
# printing original lists
print("The original list is : " + str(test_list))
# Initializing K
K = 1
# Reverse sort Matrix Row by Kth Column
# using sort() + itemgetter()
test_list.sort(key = itemgetter(K), reverse = True)
# printing result
print ("List after performing sorting of matrix records : " + str(test_list))
Output :
The original list is : [['Manjeet', 65], ['Akshat', 42], ['Akash', 38], ['Nikhil', 192]] List after performing sorting of matrix records : [['Nikhil', 192], ['Manjeet', 65], ['Akshat', 42], ['Akash', 38]]
Method 3: Using a list comprehension
Step-by-step approach:
- We first create a list comprehension that sorts the rows of the matrix based on their Kth column in descending order.
- Use the sorted() function with a list comprehension that sorts the rows of the matrix based on their Kth column in descending order. The key function for the sort is a lambda function that returns the Kth column of each row.
- The sorted() function returns a list of tuples, where the first element of each tuple is the Kth column of the corresponding row and the second element is the entire row.
- Finally, we use another list comprehension to extract only the rows from the sorted list of tuples and create a new list of rows sorted by the Kth column in descending order.
Python3
# Initializing list
test_list = [['Manjeet', 65], ['Akshat', 42], ['Akash', 38], ['Nikhil', 192]]
# printing original lists
print("The original list is : " + str(test_list))
# Initializing K
K = 1
# Reverse sort Matrix Row by Kth Column
# using list comprehension
test_list = [row for _, row in sorted([(x[K], x) for x in test_list], reverse=True)]
# printing result
print("List after performing sorting of matrix records : " + str(test_list))
OutputThe original list is : [['Manjeet', 65], ['Akshat', 42], ['Akash', 38], ['Nikhil', 192]]
List after performing sorting of matrix records : [['Nikhil', 192], ['Manjeet', 65], ['Akshat', 42], ['Akash', 38]]
Time complexity: O(n log n), where n is the number of rows in the matrix.
Auxiliary space: O(n), where n is the number of rows in the matrix.
Similar Reads
Python Tutorial - Learn Python Programming Language Python is one of the most popular programming languages. Itâs simple to use, packed with features and supported by a wide range of libraries and frameworks. Its clean syntax makes it beginner-friendly. It'sA high-level language, used in web development, data science, automation, AI and more.Known fo
10 min read
Python Interview Questions and Answers Python is the most used language in top companies such as Intel, IBM, NASA, Pixar, Netflix, Facebook, JP Morgan Chase, Spotify and many more because of its simplicity and powerful libraries. To crack their Online Assessment and Interview Rounds as a Python developer, we need to master important Pyth
15+ min read
Python OOPs Concepts Object Oriented Programming is a fundamental concept in Python, empowering developers to build modular, maintainable, and scalable applications. By understanding the core OOP principles (classes, objects, inheritance, encapsulation, polymorphism, and abstraction), programmers can leverage the full p
11 min read
Python Projects - Beginner to Advanced Python is one of the most popular programming languages due to its simplicity, versatility, and supportive community. Whether youâre a beginner eager to learn the basics or an experienced programmer looking to challenge your skills, there are countless Python projects to help you grow.Hereâs a list
10 min read
Python Exercise with Practice Questions and Solutions Python Exercise for Beginner: Practice makes perfect in everything, and this is especially true when learning Python. If you're a beginner, regularly practicing Python exercises will build your confidence and sharpen your skills. To help you improve, try these Python exercises with solutions to test
9 min read
Python Programs Practice with Python program examples is always a good choice to scale up your logical understanding and programming skills and this article will provide you with the best sets of Python code examples.The below Python section contains a wide collection of Python programming examples. These Python co
11 min read
Python Introduction Python was created by Guido van Rossum in 1991 and further developed by the Python Software Foundation. It was designed with focus on code readability and its syntax allows us to express concepts in fewer lines of code.Key Features of PythonPythonâs simple and readable syntax makes it beginner-frien
3 min read
Python Data Types Python Data types are the classification or categorization of data items. It represents the kind of value that tells what operations can be performed on a particular data. Since everything is an object in Python programming, Python data types are classes and variables are instances (objects) of thes
9 min read
Input and Output in Python Understanding input and output operations is fundamental to Python programming. With the print() function, we can display output in various formats, while the input() function enables interaction with users by gathering input during program execution. Taking input in PythonPython input() function is
8 min read
Enumerate() in Python enumerate() function adds a counter to each item in a list or other iterable. It turns the iterable into something we can loop through, where each item comes with its number (starting from 0 by default). We can also turn it into a list of (number, item) pairs using list().Let's look at a simple exam
3 min read