Lecture Notes: JavaScript Algorithms for Coding Interviews

Course Overview

• Instructor: Mukhtar from Coding Monkey.
• Objective: Prepare students for LeetCode style coding challenges, focusing on 10 key JavaScript algorithms.
• Target Audience: Beginners aiming to tackle coding interviews at big tech companies.

Key JavaScript Algorithms

1. Reversing a String and Integer

• Common Interview Question: Reversing strings or integers.
• String Reversal Example:
  • Use a loop to prepend each character.
  • Use modern JavaScript syntax for cleaner code.
  • Built-in methods: split(), reverse(), join().
• Integer Reversal:
  • Convert integer to string, reverse, then convert back.
  • Handle edge cases like negative numbers.
  • Use Math.sign and parseInt to preserve sign.

2. Palindrome Check

• Definition: A string that reads the same backward.
• Solution:
  • Reverse the string and compare.
  • Use split(), reverse(), join() to reverse.
• Optimization: Compare within a single line using JavaScript chaining.

3. Character Frequency

• Problem: Find the most commonly used character in a string.
• Solution:
  • Use an object to count character occurrences.
  • Loop through object to find maximum frequency.
  • Use Object.entries for older syntax, or for...in for cleaner code.

4. Array Chunking

• Problem: Divide an array into subarrays of specified size.
• Solution:
  • Use Array.slice() to get chunks.
  • Use a loop and increment by chunk size.

5. Capitalization

• Problem: Capitalize the first letter of each word in a string.
• Solution:
  • Split string into words.
  • Capitalize first letter of each word using toUpperCase().
  • Use Array.map() for cleaner syntax.

6. Anagram Check

• Definition: Two strings with identical character counts.
• Solution 1:
  • Build character maps for both strings.
  • Compare maps for equality.
• Solution 2 (Optimized):
  • Sort both strings and compare directly.

7. Vowel Count

• Problem: Count vowels in a string.
• Solution 1 (Regex):
  • Use String.match() with regex for vowels.
• Solution 2 (Without Regex):
  • Loop through string, check against an array of vowels.

8. FizzBuzz Challenge

• Problem: Print numbers with special rules for multiples of 3 and 5.
• Solution:
  • Use modulo operator % to check divisibility.
  • Print "Fizz", "Buzz", or "FizzBuzz" accordingly.

9. Step Shapes

• Problem: Print a step shape using pound signs.
• Solution:
  • Use nested loops to handle rows and columns.
  • Ensure correct spaces on the right.

10. Pyramid Shapes

• Problem: Print a pyramid shape with spaces on both sides.
• Solution:
  • Use nested loops recognizing midpoint for rows.
  • Ensure symmetry with spaces on left and right.

11. Spiral Matrix

• Problem: Create a spiral matrix of numbers.
• Solution:
  • Define start and end points for rows and columns.
  • Use multiple loops for each side of the matrix.
  • Use a while loop to handle inner spirals.

Bonus Material

• GitHub Repository: Access to additional coding challenges and LeetCode problems.
• Homework: Explore and use the two-pointer technique and Array.every() for problem-solving.

Additional Notes

• Practice: Try solving examples and homework assignments for better understanding.
• Resources: MDN documentation for JavaScript methods and functions.
• Advice: Incrementally build solutions; start with simpler components and expand.