Coding_questions_for_practice.md

Coding Practice Tips and Questions

You must have come across what to practice and what not when you are starting your coding career. I will be always working on this to improvement of this page by adding different types of questions.

This document covers various coding challenges and tips to improve your problem-solving skills in JavaScript. Each section focuses on a different category of questions, ranging from array manipulation to basic algorithms and data structures.

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1. Array and Object Manipulation

Merging Objects and Mapping Through Arrays

• Merge Two Objects
  Write a function that takes two objects and returns a new object with combined key-value pairs. If the same key exists in both objects, the value from the second object should overwrite the first.

• Transform Array of Objects
  Given an array of objects, return an object where keys are derived from one of the object properties, and values are arrays of objects.
  Example: Convert [{ id: 1, name: 'A' }, { id: 2, name: 'B' }] into { 1: { name: 'A' }, 2: { name: 'B' } }.

• Convert Array of Strings to Object Format
  Given an array of strings like ["apple", "banana", "cherry"], convert it into an object where each element is a key with a default value.
  Example: { "apple": 0, "banana": 0, "cherry": 0 }.

• Array Mapping
  Write a function to take an array of numbers and return an array of squared values.

• Group by Property
  Given an array of objects, group them by a specified property.
  Example: Group students by age, so [{name: 'A', age: 20}, {name: 'B', age: 20}, {name: 'C', age: 21}] becomes {20: [{name: 'A', age: 20}, {name: 'B', age: 20}], 21: [{name: 'C', age: 21}]}.

• Combine Arrays Without Duplicates
  Write a function that merges two arrays into one, ensuring there are no duplicate values.
  Example: mergeArrays([1, 2, 3], [2, 3, 4]) should return [1, 2, 3, 4].

• Nested Property Access
  Write a function to access the value of a deeply nested property in an object using a dot-separated string.
  Example: getProperty({ a: { b: { c: 5 } } }, 'a.b.c') should return 5.

• Deep Clone an Object
  Write a function to create a deep copy of a nested object without using JSON methods.

• Filter Object Keys
  Write a function to remove specified keys from an object.
  Example:
  Input: { a: 1, b: 2, c: 3 }, Keys to remove: ['b', 'c'].
  Output: { a: 1 }.

• Calculate Sum of Object Values
  Given an object with numeric values, write a function to calculate the sum of all values.
  Example:
  Input: { a: 10, b: 20, c: 30 }
  Output: 60.

2. Coding for Problem-Solving and Logic Building

• Find Duplicates in Array
  Write a function to identify duplicates in an array and return them as a new array.

• Count Frequency of Elements
  Given an array, count the frequency of each element and return an object with each element and its count.

• Longest String in Array
  Write a function to find and return the longest string in an array of strings.

• Count Vowels
  Write a function to count the number of vowels in a string.

• Flatten an Array
  Implement a function to flatten a nested array.
  Example: [1, [2, [3, 4]]] should return [1, 2, 3, 4].

• Anagram Checker
  Write a function to check if two strings are anagrams of each other.
  Example: isAnagram('listen', 'silent') should return true.

• Find Missing Number
  Given an array of n-1 numbers in the range 1 to n, find the missing number.
  Example: [1, 2, 4, 5] should return 3.

• Majority Element
  Find the element that appears more than n/2 times in an array. If no such element exists, return null.
  Example: [3, 3, 4, 2, 3, 3] should return 3.

3. Arrays and Strings: Common Operations

• Sorting an Array of Numbers
  Implement a function to sort an array of numbers in ascending or descending order.

• Filter Elements Based on Condition
  Write a function that takes an array of numbers and returns an array with only even or odd numbers.

• Reverse a String
  Write a function that takes a string and returns the reversed string.

• Binary Search in Sorted Array
  Implement a binary search to find an element in a sorted array. Return the index if found, otherwise return -1.

• Find Maximum and Minimum
  Write a function to find the maximum and minimum elements in an array.

• Unique Characters in a String
  Write a function to check if a string has all unique characters.
  Example: "hello" should return false, while "world" should return true.

• Remove Duplicates from Sorted Array
  Write a function to remove duplicates from a sorted array in place.
  Example: [1, 1, 2] should return [1, 2].

• Count Palindromic Substrings
  Given a string, count all substrings that are palindromes.
  Example: "aaa" has 6 palindromic substrings: "a", "a", "a", "aa", "aa", "aaa".

4. Basic Algorithms

• Bubble Sort Implementation
  Implement the bubble sort algorithm to sort an array of numbers.

• Selection Sort
  Implement selection sort to arrange an array of numbers in ascending order.

• Merge Sort
  Write a function that sorts an array using the merge sort algorithm.

• Binary Search
  Implement binary search for an element in a sorted array.

• Factorial with Recursion
  Write a recursive function to calculate the factorial of a given number.

5. Data Structures

• Stack Implementation
  Implement a stack in JavaScript with push, pop, and peek methods.

• Queue Implementation
  Implement a queue in JavaScript with enqueue, dequeue, and peek methods.

• Hash Map Basics
  Implement a hash map to store key-value pairs with methods like set, get, and delete.

• Palindrome Checker using Stack
  Check if a string is a palindrome by pushing characters to a stack and popping them in reverse order.

• Balanced Parentheses Checker
  Write a function to check if a string has balanced parentheses using a stack.
  Example: "(())" should return true, while "(()" should return false.

6. Logical and Math Challenges

• Fibonacci Sequence
  Write a function to generate the Fibonacci sequence up to a specified number of terms.

• Prime Number Checker
  Write a function to check if a number is prime.

• Generate Multiplication Table
  Write a function that takes a number and prints its multiplication table up to 10.

• Find Factors of a Number
  Write a function that returns all factors of a given number.

• Number Patterns
  Print number patterns like: 1 12 123 1234

• Find Greatest Common Divisor (GCD)
  Implement a function that takes two numbers and returns their GCD using recursion.