Quick Sort Algorithm in DSA Javascript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to choose the pivot element as the last element of the array.

DSA Javascript

function quickSort(arr) {
  if (arr.length <= 1) return arr;
  const pivot = arr[1];
  // rest of the code
}

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A[0]

B[1]

C[arr.length - 1]

D[Math.floor(arr.length / 2)]

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing the first element as pivot instead of the last.

Using arr.length instead of arr.length - 1.

The pivot is chosen as the last element, which is at index arr.length - 1.

2fill in blank

medium

Complete the code to partition the array by comparing elements with the pivot.

DSA Javascript

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

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A<=

B<

C>

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using greater than operator which reverses the partition logic.

Using >= or <= which includes equality and may cause incorrect swaps.

Elements less than the pivot are moved to the left side during partition.

3fill in blank

hard

Fix the error in the recursive call to quickSort to sort the left partition.

DSA Javascript

function quickSort(arr, low = 0, high = arr.length - 1) {
  if (low < high) {
    const pi = partition(arr, low, high);
    quickSort(arr, low, [1]);
    quickSort(arr, pi + 1, high);
  }
  return arr;
}

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Api - 1

Bpi

Clow

Dhigh

Attempts:

3 left

💡 Hint

Common Mistakes

Using pi instead of pi - 1 causes infinite recursion.

Using high or low incorrectly changes the partition boundaries.

The left partition ends at pi - 1, so we sort from low to pi - 1.

4fill in blank

hard

Fill both blanks to complete the recursive calls for sorting left and right partitions.

DSA Javascript

function quickSort(arr, low = 0, high = arr.length - 1) {
  if (low < high) {
    const pi = partition(arr, low, high);
    quickSort(arr, [1], pi - 1);
    quickSort(arr, pi + 1, [2]);
  }
  return arr;
}

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Alow

Bpi

Chigh

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using pi instead of low or high causes wrong partition ranges.

Using 0 instead of low or high causes incorrect sorting range.

Left partition is from low to pi - 1, right partition is from pi + 1 to high.

5fill in blank

hard

Fill all three blanks to complete the quickSort function with partitioning and recursive calls.

DSA Javascript

function quickSort(arr, [1] = 0, [2] = arr.length - 1) {
  if ([1] < [2]) {
    const pi = partition(arr, [1], [2]);
    quickSort(arr, [1], pi - 1);
    quickSort(arr, pi + 1, [2]);
  }
  return arr;
}

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Alow

Bhigh

Cpivot

Dindex

Attempts:

3 left

💡 Hint

Common Mistakes

Using pivot or index as parameter names causes confusion.

Mixing parameter names in recursive calls causes errors.

The function uses low and high as parameters and compares low < high.