# 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 ...
368 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 ...
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### 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 ...
552 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 ...
249 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 ...
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### 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 ...
563 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....
577 views

### Leetcode 3sum problem solution

The problem is: Given an integer array nums, return all the triplets [nums[i], nums[j], nums[k]] where ...
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### 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 ...
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### 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. ...
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### 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 <...
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1 vote
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### Binary search of 2D matrix

I have written code as below: ...
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### 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
336 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 ...
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### 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 ...
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1 vote
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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. ...
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### 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 ...
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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 ...
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1 vote
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### 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 ...
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### 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 ...
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1 vote
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### 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 ...
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1 vote
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### Printing subarrays ⚡

I was trying to to print all subarrays of an array in quadratic time. Here is my code: ...
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 ...
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### Algorithm for twoSum

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

### Finding the minimum element of a stack of numbers

As part of an online programming challenge, I wrote a program that implements a stack of integers, supporting adding and removing elements, finding the last inserted element, and the minimum element. ...
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1 vote
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### 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 ...
1k views

### Separating odd numbers and even numbers into two vectors in C++

I'm learning C++, and would like some guidance. I'm pretty sure I'm doing something wrong. This algorithm runs in O(n) time and uses O(n) external space. Could I make a more efficient algorithm for ...
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### Brute force to solve refund amount in a payment/invoice domain

I work at a major Swedish insurance company. I'm in charge of a service that matches bank payments with invoices. I will not show the details of that match logic. But one outcome of the match is that ...
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107 views

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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 ...
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### 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 = ...
313 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 ...
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261 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 ...
218 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 ...
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1 vote
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### URLify a given String - replace spaces with %20

I have written a code to replace all spaces in a String with %20. ...
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### 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 ...
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### 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 (...
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### 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. ...
113 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. ...
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### 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 ...
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1 vote
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### 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,...
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### 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 ...
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