# 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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### LFU cache in Kotlin

I've been working on the classic LFU (Least Frequently Used) cache running in O(1) time problem lately and, as a student, I kind of struggled with the algorithms I found online. I got most of the idea ...
369 views

### Fast and precise summation of random numbers

I'm trying to first formulate this challenge. In short, we want to sum up an stream of random numbers with the following objective: The objective is "simply" to sum up as many sequences as ...
181 views

### Hackerrank "New Year chaos" solution - permute sequence by swapping adjacent terms

I was doing the Hackerrank "New Year chaos" problem. Here is the description: It is New Year's Day and people are in line for the Wonderland rollercoaster ride. Each person wears a sticker ...
1 vote
1k views

### Leetcode 55. Jump Game solution

I was working on Jump Game problem on leetcode Question You are given an integer array nums. You are initially positioned at the array's first index, and each element in the array represents your ...
251 views

### Colorful Subgraph Dynamic Programming Solution and a Naive One

Given a graph $G(V, E)$ with vertices $V$ and edges $E$, where each vertex is associated with a single color from a set of colors $C=\{1, 2, ..., k\}$, we define the following problem: Problem ...
555 views

### Simplify complexity [closed]

I came across this question which asks to create a function which will return true/false based on the passed array containing all the letters to make up the passed word. Each letter from array can ...
69 views

### Proving a conjecture given a set of clauses - calculating complexity

I have written this Perl program to prove a conjecture given a set of clauses. I've actually posted some code from it on here in another question. This time it's all done, and I've made it as fast as ...
132 views

### Longest spell to cast from pages of spellbook follow-up

This question is from the PCTC 2022 R2 Past Paper and is a follow-up on my previous question. Previous question I have implemented several solutions suggested, such as creating an array with pages ...
567 views

### Longest spell to cast from pages of spellbook

While practicing for a school coding challenge, I came across this problem. My code got the right answers but exceeded the time limited. Any tips for how to reduce the time complexity? https://pctc....
1 vote
94 views

### Calculate maximum value of expression for potential associations

I have an algorithm that calculates the maximum value of an expression that is made from numbers and * or + by adding parentheses. It has 3 nested loops, so the time complexity should be N^3 ...
584 views

### Leetcode 3sum problem solution

The problem is: Given an integer array nums, return all the triplets [nums[i], nums[j], nums[k]] where ...
2k views

### Reverse the digits of an Integer

Reverse digits of an integer. Example1: x = 123, return 321 Example2: x = -123, return -321 Return 0 if the result overflows and does not fit in a 32 bit signed integer This is my approach: <...
494 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 ...
127 views

### Handwriting progressive drawing

Implementation to progressively draw symbols, when provided with symbol implementations it supports any type of symbols, though for the review purpose just two hand written latin symbols are supported ...
79 views

### complexity reduction (refacto) [closed]

I'm trying to reduce the complexity of this piece of code following a SonarQube error. I have several similar blocks, and even if I try to extract them into private methods, the Sonar error persists. ...
544 views

### One Piece Treasure- Find the number of palindromic substrings in a large substring

I'm trying to solve the below question: A string of characters X (all in lowercase) of length n is present. We can ask a query <...
2k 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 ...
193 views

### 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. ...
256 views

### Time and space complexity of base conversion code

I have an algorithm that performs the base conversion. The input is a string and two ints b1 and b2. The string represents an ...
3k views

### Award Budget Cuts implementation in Java

PRAMP Award Budget Cuts The awards committee of your alma mater (i.e. your college/university) asked for your assistance with a budget allocation problem they’re facing. Originally, the committee ...
114 views

### Quickselect algorithm implementation and its time-complexity

I wrote this code to find kth smallest element in the array by renowned algorithm quickselect. Here is the link where you can see the working code. What points are there to be improved? Could you ...
1 vote
106 views

### Binary search of 2D matrix

I have written code as below: ...
1 vote
340 views

### Finding highly correlated variables in a dataframe by evaluating its correlation matrix's values

I read data from Excel into a Pandas DataFrame, so that every column represents a different variable, and every row represents a different sample. I made the function below to identify potential ...
95 views

### For two sequences N and M, display counts of elements n from N below each m from M up to the first n above m

A school's task: There are two sequences n_tab and m_tab. For every element m in m_tab ...
3k views

### Finding whether there exists a pair of numbers in a set having a given product

Devise an algorithm that will operate on a number x and a set of n distinct numbers such that in $O(n \lg n)$ time, the algorithm indicates whether or not there are two numbers in the set that have ...
1 vote
23 views

### Designing a font definition with multiple variants per glyph

My project penhand tries to visualize the process of writing with a pen. Part of the project is an engine that converts text entry into a sequence of glyphs that are then rendered as animation into a ...
207 views

### Pre-calculate attacks in a chess game

I'm writing (or at least trying to write) a chess engine in C++. This is the first time I write code in C++, and I use this project to practice. Anyway, I'm following the general guidelines of a ...
160 views

I am trying to model the proof of Immerman–Szelepcsényi Theorem with Haskell since it heavily uses non-determinism. An explanation of what the point of this is can be found here. ...
58 views

### Merge Sort with Minimum Sufficient Variables, Verbosity and better Space Complexity

The majority of merge sort implementations searched online are provided with unnecessary variables and code lines. Here is an attempt to reduce that. However, does passing back the subArray as return ...
1 vote
413 views

### group countries by language in JavaScript

I need a better implementation than the below code (O(N) Solution), I am grouping countries by language ( data ) is the countries JSON, each country could have 0, 1 .. or more language as the object ...
367 views

### 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 ...
3k views

### Assignment function for Intervals container

I found the two related questions but they, however, do not answer my question: interval map implementation Where exactly does my code not adhere to the specification of the key and value type? The ...
392 views

### Number Plate Generation Program

I wrote a number plate generation program. The program generates number plates for a car registered with a specific Memory Tag and on a specific date. Number plates use the following format: (2 letter ...
459 views

### Doubly linked list first fit free list malloc/free in Python

As an exercise I've implemented malloc and free in Python as a first fit free list as described here. This tracks which blocks are free in a doubly linked list that is sorted by the address of the ...
204 views

### Program to generate a tree of permutations

There is a computation I'm doing with permutations (permutations of varying length of an entire interval [1,N] for some N) in python that I feel could be faster. ...
279 views

### Binary Search written in python with O(n) [closed]

def search(nums, target): for i in range(len(nums)): if nums[i] == target: return i if nums[i] == None: return -1 I think ...
1 vote
75 views

### Traveling salesman (Dynamic Approach) retrieve path without losing on time complexity

It is difficult to find resources on above programming problem therefore I've decided to ask a question on this forum. Using memoization and dynamic programming we can obtain a code that gives \\$O(2^N ...
421 views

### Add two numbers represented as digit strings

This algorithm adds two numbers digit by digit using their string representations. I am wondering what the time and space complexities of the following algorithm are. In particular, I am wondering ...
2k views

### Subset sum simple iterative implementation

Here is the simplest iterative implementation of Subset sum problem that I could come up with1, as a follow up to this recursive implementation of the same problem: ...
114 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 ...
1 vote
335 views

### Given the arrival times of people at a door, resolve their passage times

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 ...
1 vote
353 views

### Printing subarrays ⚡

I was trying to to print all subarrays of an array in quadratic time. Here is my code: ...
2k views

### Swift - Finding longest binary gap of a given integer

I recently had the chance to try Codility's algorithm training, and the very first one in the list is finding the longest binary gap of a given integer. I tried to implement this in Swift, and after ...
276 views

### Long arithmetic addition in JS

The implementation of the algorithm which adds two number in string form with arithmetic rules. ...
415 views

### Algorithm for twoSum

This is my PHP algorithm for the twoSum problem in leetCode: ...
95 views

### Time complexity of several methods of reversing a domain name string

Note: I'm aware of this existing post which is similar. However, it does not address all my questions sufficiently. I have the following three functions, all of which do the same thing: reverse a ...
4k views

### Find the smallest positive integer that is absent from a given array

I made the acquaintance of big-O a couple of weeks ago and am trying to get to grips with it, but although there's a lot of material out there about calculating time complexity, I can't seem to find ...
1k views

### Median of two sorted arrays

The task is to find the median of two Arrays. I have an O(n) solution. Can it be written in a better time complexity? ...