Quick Sort Partition Lomuto and Hoare in DSA Javascript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to select the pivot as the last element in Lomuto partition.

DSA Javascript

function lomutoPartition(arr, low, high) {
  let pivot = arr[1];
  let i = low - 1;
  for (let j = low; j < high; j++) {
    if (arr[j] <= pivot) {
      i++;
      [arr[i], arr[j]] = [arr[j], arr[i]];
    }
  }
  [arr[i + 1], arr[high]] = [arr[high], arr[i + 1]];
  return i + 1;
}

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

A[low]

B[high]

C[low + 1]

D[0]

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing the first element as pivot instead of the last.

Using an index outside the current subarray.

In Lomuto partition, the pivot is chosen as the last element, which is at index 'high'.

2fill in blank

medium

Complete the code to swap elements in Lomuto partition when arr[j] is less than or equal to pivot.

DSA Javascript

if (arr[j] [1] pivot) {
  i++;
  [arr[i], arr[j]] = [arr[j], arr[i]];
}

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

A<=

B>

C<

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using only '<' and missing equal elements.

Using '>' which reverses the logic.

We swap when arr[j] is less than or equal to pivot to group smaller or equal elements to the left.

3fill in blank

hard

Fix the error in the Hoare partition loop condition to correctly partition the array.

DSA Javascript

while (arr[i] [1] pivot) i++;
while (arr[j] [2] pivot) j--;

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

A<

B<=

C>=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using <= or >= which can cause infinite loops.

Swapping the comparison directions.

In Hoare partition, we move i forward while arr[i] is less than pivot, and j backward while arr[j] is greater than pivot.

4fill in blank

hard

Fill both blanks to complete the Hoare partition swap condition and return statement.

DSA Javascript

if (i >= j) return [1];
[arr[i], arr[j]] = [arr[j], arr[i]];

// Return index to split array
return [2];

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

Aj

Bi

Clow

Dhigh

Attempts:

3 left

💡 Hint

Common Mistakes

Returning i instead of j.

Returning low or high which are boundaries, not partition index.

When i >= j, we return j as the partition index in Hoare partition.

5fill in blank

hard

Fill all three blanks to complete the Lomuto partition function with correct pivot selection, swap, and return.

DSA Javascript

function lomutoPartition(arr, low, high) {
  let pivot = arr[1];
  let i = low - 1;
  for (let j = low; j < high; j++) {
    if (arr[j] [2] pivot) {
      i++;
      [arr[i], arr[j]] = [arr[j], arr[i]];
    }
  }
  [arr[i + 1], arr[high]] = [arr[high], arr[i + 1]];
  return [3];
}

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

A[high]

B<=

Ci + 1

D[low]

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong pivot index.

Using wrong comparison operator.

Returning wrong partition index.

Pivot is last element arr[high], swap when arr[j] <= pivot, and return i+1 as partition index.