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When working with strings in Python, we often need to remove duplicate characters while preserving the order of first occurrence. This is useful in data cleaning, text processing, and algorithm problems. We can solve this using an ordered dictionary to maintain the insertion order of characters. The dictionary tracks which characters we've seen, and we can join the keys to get our result string. So, if the input is like s = "bbabcaaccdbaabababc", then the output will be "bacd". Algorithm Create an ordered dictionary to store characters in insertion order For each character c in ... Read More
Suppose we have a string s of size n. We need to find all rotated strings by rotating them 1 place, 2 places, up to n places to the left. So, if the input is like s = "hello", then the output will be ['elloh', 'llohe', 'lohel', 'ohell', 'hello'] Approach To solve this, we will follow these steps − Create an empty result list Get the length of the string For each rotation from 1 to n places: Move the first character to the end Add the rotated string to the result ... Read More
Credit card numbers must follow specific formatting rules to be considered valid. We need to check if a credit card number meets all the required criteria including format, length, and digit patterns. Credit Card Validation Rules A valid credit card number must satisfy these conditions ? Start with 4, 5, or 6 Be exactly 16 digits long Contain only numeric digits May have digits grouped in four sets separated by hyphens Must not use spaces, underscores, or other separators Must not have 4 or more consecutive identical digits Implementation Here's a complete solution ... Read More
Before going to the solution let's understand about factorial. The factorial is a product of all the integers smaller than or equal to n. The mathematical representation is n! = n × (n-1) × (n-2) × ... × 1. For example, 4! = 4 × 3 × 2 × 1 = 24. In this article, let's explore different ways to find the factorial of a large number in Python. Various Methods Following are multiple ways to find the factorial of a large number in Python − Using 'math' Module ... Read More
The reduce() function in Python applies a function cumulatively to items in a sequence, reducing them to a single value. When working with rational numbers (fractions), we can use reduce() to find their product efficiently. For example, if we have fractions = [(5, 3), (2, 8), (6, 9), (5, 12), (7, 2)], the product will be 5/3 * 2/8 * 6/9 * 5/12 * 7/2 = (5*2*6*5*7)/(3*8*9*12*2) = 2100/5184 = 175/432 (in reduced form). Syntax from functools import reduce reduce(function, iterable) Algorithm Steps Create a list of Fraction objects ... Read More
Sometimes we need to find elements from a list that appear a certain number of times or more. Python provides several approaches to solve this problem using frequency counting techniques. So, if the input is like nums = [2, 5, 6, 2, 6, 1, 3, 6, 3, 8, 2, 5, 9, 3, 5, 1] k = 3, then the output will be [2, 5, 6, 3] Using Counter from collections The Counter class provides an efficient way to count element frequencies ? from collections import Counter def solve(nums, k): c ... Read More
Email validation is a common requirement in web applications. We need to check whether an email address follows the correct format and character rules. Python's re module provides powerful regular expression capabilities for this task. Email Validation Rules A valid email must follow these conditions ? Format must be username@company.domain Username can contain letters, numbers, dashes, and underscores Company name can contain letters and numbers only Domain can contain lowercase letters only Domain extension length must be 1-3 characters ... Read More
Suppose we have a number x and another number n. We have to find the number of ways we can get x as the sum of nth power of some unique numbers. So, if the input is like x = 100, n = 2, then the output will be 3 because the possible solutions are: 6² + 8² = 36 + 64 = 100 10² = 100 1² + 3² + 4² + 5² + 7² = 1 + 9 + 16 + 25 + 49 = 100 Algorithm To solve this problem, we ... Read More
Sorting strings in a custom order requires defining a special key function. In this problem, we need to sort an alphanumeric string with specific priority rules for different character types. Sorting Rules The custom sorting follows this priority order: All sorted lowercase letters come first All sorted uppercase letters come second All sorted odd digits come third All sorted even digits come last For example, if the input is "HeLlo1234", the output will be "eloHL1324". Custom Key Function We create a key function that assigns priority codes to different character types ? ... Read More
Suppose we have a 2D list containing information about athletes. This information includes rank, age, and height. Each row contains data for different athletes. We need to sort the table based on a given attribute index k. So, if the input is like ? Rank Age Height 1 25 190 2 35 180 3 33 185 4 26 175 5 35 180 And k = 1 (sort by age), then the output will be ? ... Read More