Binary Search Iterative Approach in DSA Javascript - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Binary Search for Existing Element

What is the output of the following JavaScript code that performs an iterative binary search for the number 7 in a sorted array?

DSA Javascript

function binarySearch(arr, target) {
  let left = 0;
  let right = arr.length - 1;
  while (left <= right) {
    let mid = Math.floor((left + right) / 2);
    if (arr[mid] === target) {
      return mid;
    } else if (arr[mid] < target) {
      left = mid + 1;
    } else {
      right = mid - 1;
    }
  }
  return -1;
}

const array = [1, 3, 5, 7, 9, 11];
console.log(binarySearch(array, 7));

A -1

B 3

C 2

D 4

💡 Hint

Remember that array indices start at 0 and the array is sorted.

The number 7 is at index 3 in the array [1, 3, 5, 7, 9, 11]. The binary search finds it and returns the index 3.

❓ Predict Output

intermediate

Output of Binary Search for Non-Existing Element

What is the output of the following JavaScript code that performs an iterative binary search for the number 7 in a sorted array?

DSA Javascript

function binarySearch(arr, target) {
  let left = 0;
  let right = arr.length - 1;
  while (left <= right) {
    let mid = Math.floor((left + right) / 2);
    if (arr[mid] === target) {
      return mid;
    } else if (arr[mid] < target) {
      left = mid + 1;
    } else {
      right = mid - 1;
    }
  }
  return -1;
}

const array = [2, 4, 6, 8, 10];
console.log(binarySearch(array, 7));

A 0

B 3

C 2

D -1

💡 Hint

If the target is not found, the function returns -1.

The number 7 is not in the array [2, 4, 6, 8, 10], so the function returns -1.

🧠 Conceptual

advanced

Why Use Iterative Binary Search Instead of Recursive?

Which of the following is the main advantage of using an iterative binary search over a recursive binary search?

A Iterative binary search always runs faster than recursive binary search in all cases.

B Iterative binary search is easier to write and understand than recursive binary search.

C Iterative binary search uses less memory because it avoids the overhead of recursive calls.

D Iterative binary search can handle unsorted arrays without sorting them first.

💡 Hint

Think about how function calls use memory.

Recursive calls add overhead to the call stack, which uses more memory. Iterative binary search uses a loop and constant memory.

🔧 Debug

advanced

Identify the Bug in Binary Search Implementation

What is the output of the following JavaScript code when searching for 5 in the array?

DSA Javascript

function binarySearch(arr, target) {
  let left = 0;
  let right = arr.length;
  while (left <= right) {
    let mid = Math.floor((left + right) / 2);
    if (arr[mid] === target) {
      return mid;
    } else if (arr[mid] < target) {
      left = mid + 1;
    } else {
      right = mid - 1;
    }
  }
  return -1;
}

const array = [1, 3, 5, 7, 9];
console.log(binarySearch(array, 5));

A Returns 2 (correct index)

B Returns -1 (target not found)

C SyntaxError: Unexpected token

D TypeError: Cannot read property 'undefined' of undefined

💡 Hint

Check the initial value of the right pointer and array indexing.

The code returns 2 (correct index) because the target is found at mid=2 on the first iteration. However, right = arr.length is a bug: it risks out-of-bounds access to arr[arr.length] (undefined in JS).

🚀 Application

expert

Number of Iterations in Binary Search

Given a sorted array of length 31, what is the maximum number of iterations the iterative binary search algorithm will perform to find a target or conclude it is not present?

A 5

B 4

C 6

D 31

💡 Hint

Binary search halves the search space each iteration. Think about powers of 2.

Binary search reduces the search space by half each iteration. For 31 elements, maximum iterations = ceil(log2(31)) = 5.