# Questions tagged [complexity]

Complexity is the analysis of how the time and space requirements of an algorithm vary according to the size of the input. Use this tag for reviews where the "Big O" is a concern.

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### Find the highest product of three numbers in a list (Python)

I wrote the below as a solution to: Problem Find the highest product of three numbers in a list Constraints Is the input a list of integers? Yes Can we get negative inputs? Yes Can there be ...
104 views

### SumList Cracking the coding Interview

Sum of 2 numbers, represented with linked lists, where digits are in backward order or forward order. Backward order Example INPUT:(7->1->6) + (5->9->2) = 617+295 OUTPUT: 2->1->9 = ...
55 views

### Optimizing methods with multiple if checks on getter values

I have a method where I fetch user input, check if certain values exist, and based on that build my own custom input object that I would use to search in a database. The code for the search method is ...
94 views

### Find the largest decrease in a sequence of numbers

I have written a function that takes as input a list of 5 numbers, then the program's goal is to return the largest drop in the list. It is important to understand that [5, 3, ...] is a decrease of 2 ...
89 views

### Finding unique top sums from multiple lists

My question arises from this post on MSE where I have provided an answer to solve the question : There are multiple lists given. The number of lists is arbitrary. Each list contains numbers and is ...
141 views

### URLify a given String - replace spaces with %20

I have written a code to replace all spaces in a String with %20. ...
127 views

### Can I further optimize this solution for HackerRank's “Making Candies”?

My C++ solution for HackerRank's "Making Candies" problem, reproduced below, is as optimized as I can make it and appears similar to what others say are optimal solutions. However, six of ...
95 views

### Substring search in Java

I am trying to make an algorithm that will find the index of a given substring (which I have labeled pattern) in a given String (...
64 views

### Speed-up anomaly detection for pandas dataframes with vectorized operations

Motivation: I very often face a task where I need to check that dataframe's values are correct or not. Based on it I can create another dataframe with True/False values which are based on the first ...
66 views

### Optimize nested loops for counting the total number of selections

The question is: To select 2 numbers out of n positive integer inputs (order matters), where the number that is placed anywhere before the second must be greater than the second by a given number m. ...
53 views

### Monotonic stack - complexity analysis

I tried following the official solution of LC975 (https://leetcode.com/problems/odd-even-jump/), using a monotonic stack - i.e., I reimplemented their solution (Approach 1) from python in C++. TLDR ...
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### Is this an efficient/correct way to get largest Prime factor?

Is this an efficient way to get the largest prime factor of a given number? Other solutions I found involved nested algorithms. ...
120 views

### strstr implementation with python and sets

Please review my strstr implementation in terms of time/space efficiency and overall readability. I am preparing for a coding assessment coming up as I am looking to pivot my career from Physics to ...
57 views

### Sorting Algorithm using Modified Merge sort

I've been messing around with merge sort. Instead of doing a recursive division of the array I chose to keep keep track of the middle index of every three numbers. Using the index of the middle number,...
1k views

### Merge arrays in objects in array based on property

I have the following code which takes an array that might have duplicate ids and will merge the items of those duplicate, and ...
134 views

### Performant Sort function for big arrays

In sort(arr), I want to sort an array. Children must be beneath their parent. And children of the same parent are sorted using ...
317 views

### LeetCode 3Sum Java Solution

I have this Java solution to LeetCode's 3Sum problem. I would be really grateful if I could get feedback on correctness, scalability, efficiency, coding best practices, and OOP design. I'm relatively ...
83 views

### 2D Array Word Search: Complexity and Optimization

🧩 Objective Determine whether a given word is contained in a 2D Array word search. 🔎 Question 1. What are the time and space complexities of the current algorithm? Time complexity Linear: \\$O(2(r * ...
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### Generate unique string permutations recursively

🧩 Objective Write a recursive method for generating all permutations of an input string. Return them as a set. See: Recursive String Permutations - Interview Cake 🔎 Questions 1: How does the ...
276 views

### Most efficient solution for USACO: Cow Gymnastics - Python

I was trying to figure out this problem, and I did. However, my code is so abhorrently ugly that I want to tear out my eyeballs when I look at it: ...
90 views

### Cyclomatic Complexity (complexity)

I have a program for finding shortest distance/path and I got a correct answer but I am getting an issue i.e., "Function 'shortestPath' has a complexity of 9. Maximum allowed is 6." This is ...
77 views

### Ensuring if an object is Assignable from a class type

I am trying to ensure type in the below method. How to reduce its cognitive complexity to below 15 from the current 27? It looks more readable as it is? Is there a way to break this down to make it ...
145 views

### 01 Matrix is too slow when solved using DFS

I tried solving Leetcode 01 Matrix problem. It is running too slow when solved using DFS approach. Given a matrix consists of 0 and 1, find the distance of the nearest 0 for each cell. The distance ...
409 views

### Most Efficient Solution for USACO: Triangles - Python

I'm trying to solve this problem with Python 3.8. In my code, I used 3 nested for loops to check every single point and storing the largest area with each set of points. This program works fine, but ...
295 views

### Best Algorithm for solving USACO: Photoshoot - Python

I was trying to solve this problem with Python 3.8. I couldn't find a way other than to brute-force calculate all the possible permutations then check which permutation was valid. The program works ...
52 views

### What is the time complexity problem I need to manage on a Hackerank “Ransom Note” - my code runs perfectly [closed]

I am trying to solve the "Ransom Note" problem on hackerank. Why isn't my code getting submitted? What can I do differently? is my total time complexity, in this case, it is O(n^2)? ...
572 views

### Dynamic Array Based Stack in C

I wrote a dynamic stack in C that uses an array as a structure. I tried to maintain O(1) for push and pop and believe I have done so. I want to know what can be written in a cleaner way and if there ...
37 views

### Count number of square integers in a given range of ints (faster function?)

The function below passes most test cases: ...
117 views

### Car Pooling algorithm time complexity

I created a solution for the car pooling algorithm. Problem: You are driving a vehicle that has capacity empty seats initially available for passengers. The vehicle only drives east (ie. it cannot ...
129 views

### Determine the complexity of sorting a binary array

The challenge is to sort an integer array containing only ones and zeros with the lowest complexity possible. As always, I am interested in any improvements suggested but in this question I am most ...
69 views

### Closest Pair heuristics, graph with adjacency matrix in C++17

I was trying to solve a problem that was briefly mentioned at the beginning of the "The Algorithm Design Manual" by Steven Skiena (Ch 1, Problem 26). It took me some time to build a working ...
4k views

### The fastest way to find one unique value when all other values are the same

I have completed this question and I am wondering what is the fastest way to solve it. The question is "There is an array with some numbers. All numbers are equal except for one. Try to find it!&...
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### Benchmarking multiple implementations of a Code Kata: queue for the self-checkout tills at the supermarket

I was reading this question: Why is my function timing out when run with a larger data set? And although I couldn't quite grasp the OP's implementation and so didn't feel like answering. I did some ...
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### Parser for file made up of sections

I'm parsing a file made up of various sections. I have a current_section variable that tracks which portion of the file I'm currently processing and the following <...
1k views

### Computing the item price and vat for a given pricing, order, and exchange rate

How can I improve the readability of the below function using a list comprehension? Also, is there a way to improve items() performance? ...
34 views

### Improving time complexity for Count the Islands DFS

For game AI development, I am currently using a slight modification on the DFS "count the islands" problem (specification below) as a solution to the ...
45 views

This code unzips the downloaded subtitle files and maps them to their corresponding video file. Currently, after pairing video files with their corresponding subtitle files, it links them by renaming ...
74 views

### Faster binary search to find the index in Python?

I am implementing a binary search algorithm and my code is as shown bellow: ...
609 views

### Time and Space Complexity of Prime factorization

I have written a function that prints all the prime factors for a given number. Here is my code ...
324 views

### LeetCode: Roman to Integer in Java

I tried solve this easy leetcode challenge in java. Challenge link Here is my solution ...
4k views

### Counting Balanced numbers in a given array

I am trying a code challenge. Here is the problem description: When an element is deleted from an array, the higher-indexed elements shift down one index to fill the gap. A "balancing element&...
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### Time and Space Complexity of Leetcode Problem #31. Next Permutation

The question is as follows: Given a collection of distinct integers, return all possible permutations. Example: ...
142 views

### Refactor Java code

I was trying to solve the following question: You are given 2 arrays: one representing the time people arrive at a door and other representing the direction they want to go(in or out) You have to ...
35 views

### What is the optimal way to retrieve a list of sorted dates in a list of sorted periods in python?

Suppose I have a list with N sorted dates and M non-overlapping sorted periods with start date, end date (inclusive), and a tax rate for example. I have to make an efficient algorithm retrieve all tax ...
39 views

### Why is my function timing out when run with a larger data set?

I am working on a Code Kata ...
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### Finding the closest pair of numbers which add to a target number

This function takes two lists of same length and a target number: the number which is to be summed. The function then returns a list of pairs whose sum is closest to the target number than any other ...
113 views

### Python: Find pairs of numeric palindromes that sum up to another palindrome

I am trying to identify and print pairs of 4 digit palindromes that sum up to a 5 digit palindrome. This is what I have so far ...
2k views

### Are the sum of two numbers desired?

Given two input arrays [-1, 8, 3] and [3, 7, 2] your function will return true if any two of the numbers in the first array add ...