Counting Sort Algorithm in DSA Javascript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the count array with zeros.

DSA Javascript

const count = new Array(max + 1).fill([1]);

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

A0

B1

Cnull

Dundefined

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 instead of 0 causes incorrect counts.

Using null or undefined causes errors when incrementing.

Counting sort uses a count array initialized with zeros to store frequencies.

2fill in blank

medium

Complete the code to count the frequency of each element in the input array.

DSA Javascript

for (let i = 0; i < arr.length; i++) {
  count[arr[i]] [1];
}

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A=

B--

C++

D+=

Attempts:

3 left

💡 Hint

Common Mistakes

Using -- decreases the count incorrectly.

Using = overwrites the count instead of incrementing.

We increment the count for each element found in the input array.

3fill in blank

hard

Fix the error in the code to compute the cumulative count correctly.

DSA Javascript

for (let i = 1; i <= max; i++) {
  count[i] = count[i] [1] count[i - 1];
}

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

A-

B+

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction causes wrong cumulative counts.

Using multiplication or division is incorrect here.

Cumulative count is the sum of current count and previous counts.

4fill in blank

hard

Fill both blanks to place elements in the output array in stable order.

DSA Javascript

for (let i = arr.length - 1; i >= 0; i--) {
  output[count[arr[i]] [1]] = arr[i];
  count[arr[i]] [2];
}

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

A- 1

B+ 1

C--

D++

Attempts:

3 left

💡 Hint

Common Mistakes

Not subtracting 1 causes index errors.

Incrementing count instead of decrementing breaks stability.

We place the element at index count[element] - 1 and then decrement the count.

5fill in blank

hard

Fill all three blanks to copy the sorted output back to the original array.

DSA Javascript

for (let i = 0; i < arr.length; ) {
  arr[[1]] = output[[2]];
  [3];
}

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

Ai

Ci++

D++i

Attempts:

3 left

💡 Hint

Common Mistakes

Using different indices causes wrong copying.

Forgetting to increment i causes infinite loop.

We copy each element from output to arr using index i and increment i.