Coin Change Total Number of Ways in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the dp array with zeros.

DSA Typescript

const dp: number[] = new Array([1]).fill(0);

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Acoins.length

Bamount + 1

Camount

Dcoins.length + 1

Attempts:

3 left

💡 Hint

Common Mistakes

Using coins.length instead of amount + 1 for dp size.

Forgetting to add 1 to amount for dp array length.

We need dp array size to be amount + 1 to cover all amounts from 0 to amount.

2fill in blank

medium

Complete the code to set the base case for dp.

DSA Typescript

dp[0] = [1];

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Aamount

B0

C1

D-1

Attempts:

3 left

💡 Hint

Common Mistakes

Setting dp[0] to 0 which means no ways to make zero amount.

Setting dp[0] to amount which is incorrect.

There is exactly one way to make amount 0: use no coins.

3fill in blank

hard

Fix the error in the inner loop condition to avoid out-of-bound errors.

DSA Typescript

for (let j = coin; j [1] dp.length; j++) {

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A<

B<=

C>

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<=' causes index out of bounds error.

Using '>' or '>=' causes the loop to never run or run incorrectly.

The loop should run while j is less than dp.length to avoid index out of bounds.

4fill in blank

hard

Fill both blanks to correctly update dp array inside the loop.

DSA Typescript

dp[j] = dp[j] [1] dp[j [2] coin];

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A+

B-

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction or multiplication instead of addition.

Using j + coin instead of j - coin inside dp index.

We add the ways to make amount j and ways to make amount j - coin.

5fill in blank

hard

Fill all three blanks to complete the function that returns total ways to make amount.

DSA Typescript

function change(amount: number, coins: number[]): number {
  const dp: number[] = new Array([1]).fill(0);
  dp[0] = [2];
  for (const coin of coins) {
    for (let j = coin; j [3] dp.length; j++) {
      dp[j] = dp[j] + dp[j - coin];
    }
  }
  return dp[amount];
}

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

Aamount + 1

B1

C<

Dcoins.length

Attempts:

3 left

💡 Hint

Common Mistakes

Wrong dp array size.

Incorrect base case value.

Wrong loop condition causing errors.

dp array size is amount + 1, base case dp[0] = 1, loop runs while j < dp.length.