Binary Search Recursive Approach in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to calculate the middle index in the recursive binary search.

DSA Typescript

function binarySearch(arr: number[], target: number, left: number, right: number): number {
  if (left > right) return -1;
  const mid = Math.floor((left [1] right) / 2);
  if (arr[mid] === target) return mid;
  else if (arr[mid] < target) return binarySearch(arr, target, mid + 1, right);
  else return binarySearch(arr, target, left, mid - 1);
}

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

A-

B+

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using '-' instead of '+' causes wrong mid calculation.

Using '*' or '/' between left and right is incorrect.

The middle index is calculated by adding left and right, then dividing by 2. So the operator between left and right is '+'.

2fill in blank

medium

Complete the code to check if the target is found at the middle index.

DSA Typescript

if (arr[[1]] === target) return mid;

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

Aleft

Bright

Cmid

Dtarget

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'left' or 'right' instead of 'mid' causes wrong element check.

Using 'target' as index causes error.

We compare the element at the middle index 'mid' with the target to check if it's found.

3fill in blank

hard

Fix the error in the recursive call when the target is greater than the middle element.

DSA Typescript

else if (arr[mid] < target) return binarySearch(arr, target, [1], right);

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

Amid + 1

Bmid - 1

Cleft

Dright + 1

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'mid - 1' searches the left half incorrectly.

Using 'right + 1' goes out of bounds.

When target is greater than middle element, search in the right half starting from mid + 1.

4fill in blank

hard

Fill both blanks to complete the base case and recursive call for the left half search.

DSA Typescript

if ([1] > right) return -1;
else return binarySearch(arr, target, left, [2]);

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

Aleft

Bright

Cmid - 1

Dmid + 1

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping left and right in base case causes infinite recursion.

Using mid + 1 instead of mid - 1 searches wrong half.

The base case checks if left is greater than right. The recursive call searches left half up to mid - 1.

5fill in blank

hard

Fill all three blanks to complete the recursive binary search function.

DSA Typescript

function binarySearch(arr: number[], target: number, left: number, right: number): number {
  if ([1] > right) return -1;
  const mid = Math.floor((left [2] right) / 2);
  if (arr[mid] === target) return mid;
  else if (arr[mid] < target) return binarySearch(arr, target, mid [3] 1, right);
  else return binarySearch(arr, target, left, mid - 1);
}

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

Aleft

B+

C-

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using '-' instead of '+' in mid calculation causes wrong index.

Using mid - 1 instead of mid + 1 for right half causes infinite recursion.

Base case checks if left > right. Middle index is (left + right) / 2. Right half search starts at mid + 1.