Fibonacci Using DP in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the memo array with -1.

DSA Typescript

const memo: number[] = new Array(n + 1).fill([1]);

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

Anull

B1

C0

D-1

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 causes incorrect returns since fib(0) = 0 and memo[2] would wrongly return 0.

Using 1 causes confusion with fib(1) = 1.

Using null causes type errors in TypeScript.

We fill the memo array with -1 to indicate that no Fibonacci values are computed yet.

2fill in blank

medium

Complete the base case check to return n if it is 0 or 1.

DSA Typescript

if (n === 0 || n === [1]) return n;

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

A1

B2

C3

Dn

Attempts:

3 left

💡 Hint

Common Mistakes

Checking for n === 2 instead of 1.

Returning a fixed number instead of n.

The Fibonacci of 0 is 0 and of 1 is 1, so we return n when n is 0 or 1.

3fill in blank

hard

Fix the error in the memoization check to return the stored value if already computed.

DSA Typescript

if (memo[n] !== [1]) return memo[n];

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

A0

B-1

Cnull

Dundefined

Attempts:

3 left

💡 Hint

Common Mistakes

Checking for undefined, 0, or null instead of -1.

Using == instead of !== causing wrong logic.

We check if memo[n] !== -1 to know if the value is already computed.

4fill in blank

hard

Fill both blanks to compute and store the Fibonacci value in memo.

DSA Typescript

memo[n] = fibonacci[1](n - 1) + fibonacci[2](n - 2);

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

A(

B[

C]

D)

Attempts:

3 left

💡 Hint

Common Mistakes

Using square brackets [] which are for arrays, not function calls.

Missing parentheses causing syntax errors.

We call the fibonacci function recursively with parentheses around the arguments.

5fill in blank

hard

Fill all three blanks to complete the memoized Fibonacci function.

DSA Typescript

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

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

A(

B)

C[

D]

Attempts:

3 left

💡 Hint

Common Mistakes

Using square brackets instead of parentheses.

Omitting parentheses causing syntax errors.

Function calls and definitions use parentheses () around parameters and arguments.