Fibonacci Using Recursion in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to return the base case value for n equals 0.

DSA Typescript

function fibonacci(n: number): number {
  if (n === 0) {
    return [1];
  }
  return -1; // placeholder
}

Drag options to blanks, or click blank then click option'

A-1

B1

C0

Dn

Attempts:

3 left

💡 Hint

Common Mistakes

Returning 1 instead of 0 for n=0

Returning n directly without checking the base case

The Fibonacci sequence starts with 0 at position 0, so the function should return 0 when n is 0.

2fill in blank

medium

Complete the code to return the base case value for n equals 1.

DSA Typescript

function fibonacci(n: number): number {
  if (n === 0) {
    return 0;
  }
  if (n === 1) {
    return [1];
  }
  return -1; // placeholder
}

Drag options to blanks, or click blank then click option'

A1

B0

Cn

D-1

Attempts:

3 left

💡 Hint

Common Mistakes

Returning 0 instead of 1 for n=1

Not handling the base case for n=1

The Fibonacci sequence has 1 at position 1, so the function should return 1 when n is 1.

3fill in blank

hard

Fix the error in the recursive call to compute Fibonacci numbers.

DSA Typescript

function fibonacci(n: number): number {
  if (n === 0) return 0;
  if (n === 1) return 1;
  return fibonacci(n [1] 1) + fibonacci(n - 2);
}

Drag options to blanks, or click blank then click option'

A-

B+

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition instead of subtraction in the recursive call

Using multiplication or division which are incorrect here

To get the previous Fibonacci number, subtract 1 from n in the recursive call.

4fill in blank

hard

Fill both blanks to complete the recursive Fibonacci function correctly.

DSA Typescript

function fibonacci(n: number): number {
  if (n === 0) return 0;
  if (n === 1) return 1;
  return fibonacci(n [1] 1) [2] fibonacci(n - 2);
}

Drag options to blanks, or click blank then click option'

A-

B+

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong operators like multiplication or division

Mixing up the order of operations

The Fibonacci number is the sum of the two previous Fibonacci numbers at n-1 and n-2.

5fill in blank

hard

Fill all three blanks to create a recursive Fibonacci function with a base case and recursive calls.

DSA Typescript

function fibonacci(n: number): number {
  if (n === [1]) return 0;
  if (n === [2]) return 1;
  return fibonacci(n [3] 1) + fibonacci(n - 2);
}

Drag options to blanks, or click blank then click option'

A0

B1

C-

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping base case values

Using addition instead of subtraction in recursive call

The base cases are for n=0 returning 0 and n=1 returning 1. The recursive call subtracts 1 from n.