JavaScript Algorithms and Data Structures

An algorithm is a series of step-by-step instructions that describe how to do something.

To write an effective algorithm, it helps to break a problem down into smaller parts and think carefully about how to solve each part with code.

This repository contains JavaScript based examples that will teach you the fundamentals of algorithmic thinking by writing functions that do everything from converting temperatures to handling complex 2D arrays.

All of these examples are from FreeCodeCamp's course.

Table of Contents

• Basic Algorithm Scripting
  • 1. Convert Celsius to Fahrenheit
  • 2. Reverse a String
  • 3. Factorialize a Number
  • 4. Find the Longest Word in a String
  • 5. Return Largest Numbers in Arrays Passed

Basic Algorithm Scripting

1. Convert Celsius to Fahrenheit

Difficulty: Beginner

The algorithm to convert from Celsius to Fahrenheit is the temperature in Celsius times 9/5, plus 32.

You are given a variable celsius representing a temperature in Celsius. Use the variable fahrenheit already defined and assign it the Fahrenheit temperature equivalent to the given Celsius temperature. Use the algorithm mentioned above to help convert the Celsius temperature to Fahrenheit.

---

Solution

function convertToF(celsius) {
  let fahrenheit = (celsius * 9) / 5 + 32;
  return fahrenheit;
}

convertToF(30);

2. Reverse a String

Difficulty: Beginner

Reverse the provided string.

You may need to turn the string into an array before you can reverse it.

Your result must be a string.

---

Solution 1

function reverseString(str) {
  return str.split("").reverse().join("");
}

reverseString("hello");

Solution 2

function reverseString(str) {
  let reversedString = "";
  for (let i = str.length - 1; i >= 0; i--) {
    reversedString += str[i];
  }
  return reversedString;
}

reverseString("hello");

3. Factorialize a Number

Difficulty: Beginner

Return the factorial of the provided integer.

If the integer is represented with the letter n, a factorial is the product of all positive integers less than or equal to n.

Factorials are often represented with the shorthand notation n!

For example: 5! = 1 _ 2 _ 3 _ 4 _ 5 = 120

Only integers greater than or equal to zero will be supplied to the function.

---

Solution 1

function factorialize(num) {
  if (num === 0) {
    return 1;
  } else return num * factorialize(num - 1);
}

factorialize(5);

Solution 2

function factorialize(num) {
  let factorializedNumber = 1;
  for (let i = 2; i <= num; i++) {
    factorializedNumber *= i;
  }
  return factorializedNumber;
}

factorialize(5);

4. Find the Longest Word in a String

Difficulty: Beginner

Return the length of the longest word in the provided sentence.

Your response should be a number.

---

Solution

function findLongestWordLength(str) {
  let splitWords = str.split(" ");
  let longestWordLength = 0;

  for (let i = 0; i < splitWords.length; i++) {
    if (splitWords[i].length > longestWordLength) {
      longestWordLength = splitWords[i].length;
    }
  }
  return longestWordLength;
}

findLongestWordLength("The quick brown fox jumped over the lazy dog");

5. Return Largest Numbers in Arrays Passed

Difficulty: Beginner

Return an array consisting of the largest number from each provided sub-array. For simplicity, the provided array will contain exactly 4 sub-arrays.

Remember, you can iterate through an array with a simple for loop, and access each member with array syntax arr[i].

Solution 1

function largestOfFour(arr) {
  let results = [];
  for (let i = 0; i < arr.length; i++) {
    let largestNumber = arr[i][0];
    for (let j = 1; j < arr[i].length; j++) {
      if (arr[i][j] > largestNumber) {
        largestNumber = arr[i][j];
      }
    }
    results[i] = largestNumber;
  }
  return results;
}

largestOfFour([
  [4, 5, 1, 3],
  [13, 27, 18, 26],
  [32, 35, 37, 39],
  [1000, 1001, 857, 1],
]);

Solution 2

function largestOfFour(arr) {
  let results = [];
  arr.forEach((elements) => {
    let largestNumber = elements[0];
    elements.forEach((item) => {
      item > largestNumber && (largestNumber = item);
    });
    results.push(largestNumber);
  });
  return results;
}

largestOfFour([
  [4, 5, 1, 3],
  [13, 27, 18, 26],
  [32, 35, 37, 39],
  [1000, 1001, 857, 1],
]);