FiveEightyEight / 5.2-DSA-Assessment

DSA Assessment

Question 1

Can you explain big O notation and why it's important?

Question 2

Please rank the following Big-O functions from fastest to slowest:

O(n), O(n log n), O(1), O(n^2), O(2^n)

Question 3

What's the time complexity of the following function?

What is the time complexity, expressed in big O notation, of the below function? This function, scrambleString, accepts a string as an argument and returns that a string with the letters randomly rearranged.

function scrambleString(str) {
  let split = str.split("");

  split.forEach((char, idx) => {
    let randInd = Math.floor(Math.random() * split.length);
    split[idx] = split[randInd];
    split[randInd] = char;  
  });
  
  return split.join("");
}

Question 4

What's the time complexity of the following function?

What is the time complexity, expressed in big O notation, of the below function? This function, infiltrate, accepts an array as an argument. It creates an object called secretAgent and replaces a random index of an array with that object. It then returns the array.

const infiltrate = (arr) => {
  const secretCode = Math.floor(Math.random() * Math.random() * 1000);
  const secretAgent = {
    codename: "Duchess",
    secret: secretCode
  };
  const randomInd = Math.floor(Math.random() * arr.length);

  arr[randomInd] = secretAgent;

  return arr;
}

Question 5

Which sorting algorithm is faster: Bubble Sort or Merge Sort?

Question 6

What is the name of the algorithm that is taking place in this diagram?

Question 7

You are building a phonebook online. You want users to search for a user and find their associated phone number. What data structure what be best to model your data and why?

Question 8

Given the following code implement the pretty print method of a Linked List:

Code:

class Node {
  constructor(value) {
    this.value = value;
    this.next = null;
  }
}

class LinkedList {
  constructor() {
    this.head = null;
    this.length = 0;
  }
}

Pretty Print Output:

Console Log:
-> 1 -> 2 -> 3 -> null

Question 9

Given the following code implement the Queue data structure with the following methods:

• enqueue(value) : Add new element to the end of the queue.
• dequeue() : Removes element from beginning of the queue and returns it.
• peek() : Returns the element from beginning of the queue without removing it.
• isEmpty() : Returns a boolean indicating if the queue is empty or not.

Code:

class Queue {
  constructor() {
    this.arr = [];
  }
}

Question 10

Describe the following:

• What is a Hash Function is?
• What is a flaw with the Hashing function below:

function hash(key) {
  let sum = 0;
  for (let i = 0; i < key.length; i++) {
    sum += key.charCodeAt(i);
  }
  return sum;
}

hash("Sally"); // 517
hash("Dean");  // 376
hash("Dane");  // 376

Question 11

Name a LIFO data structure and explain how it works.

Question 12

What kind of data structure would perfectly organize the following data? Also explain why this kind of data structure would be useful.

Question 13

Define a recursive function that returns the Nth fibonnaci number.

The fibonnaci sequence works like the following:

• Fibonacci sequence: [0, 1, 1, 2, 3, 5, 8, 13, 21] and fib(4), the result would be equal to 3

Example:

console.log(fib(1)) // 1
console.log(fib(2)) // 1
console.log(fib(3)) // 2
console.log(fib(4)) // 3

Question 14

Define a recursive function that returns the factorial of a number.

If your number is 5, you would have:

5! = 5 * 4 * 3 * 2 * 1

The pattern:

0! = 1
1! = 1
2! = 2 * 1
3! = 3 * 2 * 1
4! = 4 * 3 * 2 * 1
5! = 5 * 4 * 3 * 2 * 1