Binary Search vs Linear Search Real Cost Difference in DSA Javascript - Compare & Choose

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Linear Search on an Unsorted Array

What is the output of the following JavaScript code that performs a linear search for the number 7 in an unsorted array?

DSA Javascript

const arr = [3, 1, 4, 7, 5];
function linearSearch(array, target) {
  for (let i = 0; i < array.length; i++) {
    if (array[i] === target) {
      return i;
    }
  }
  return -1;
}
console.log(linearSearch(arr, 7));

A 4

B -1

C 3

D 0

💡 Hint

Remember linear search checks each element until it finds the target.

The function checks each element in order. The number 7 is at index 3 in the array, so it returns 3.

❓ Predict Output

intermediate

Output of Binary Search on a Sorted Array

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

DSA Javascript

const arr = [1, 3, 4, 5, 7, 9];
function binarySearch(array, target) {
  let left = 0;
  let right = array.length - 1;
  while (left <= right) {
    const mid = Math.floor((left + right) / 2);
    if (array[mid] === target) {
      return mid;
    } else if (array[mid] < target) {
      left = mid + 1;
    } else {
      right = mid - 1;
    }
  }
  return -1;
}
console.log(binarySearch(arr, 7));

A 4

B -1

C 3

D 5

💡 Hint

Binary search finds the middle element and narrows down the search.

The number 7 is at index 4 in the sorted array, so the binary search returns 4.

🧠 Conceptual

advanced

Why Binary Search Requires a Sorted Array

Why does binary search require the array to be sorted to work correctly?

A Because it compares the target with the middle element to decide which half to search next, which only works if the array is sorted.

B Because binary search checks every element one by one, so sorting helps speed it up.

C Because binary search uses hashing which requires sorted data.

D Because binary search only works on arrays with unique elements.

💡 Hint

Think about how binary search decides where to look next.

Binary search compares the target with the middle element and decides to search left or right half. This logic only works if the array is sorted.

❓ Predict Output

advanced

Output of Binary Search on an Unsorted Array

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

DSA Javascript

const arr = [7, 3, 1, 4, 5];
function binarySearch(array, target) {
  let left = 0;
  let right = array.length - 1;
  while (left <= right) {
    const mid = Math.floor((left + right) / 2);
    if (array[mid] === target) {
      return mid;
    } else if (array[mid] < target) {
      left = mid + 1;
    } else {
      right = mid - 1;
    }
  }
  return -1;
}
console.log(binarySearch(arr, 7));

A 2

B -1

C 0

D 3

💡 Hint

Binary search assumes the array is sorted, but here it is not.

Because the array is not sorted, binary search cannot reliably find the target. It returns -1 indicating not found.

🧠 Conceptual

expert

Real Cost Difference Between Linear and Binary Search

Which statement best describes the real cost difference between linear search and binary search when searching for an element in a large sorted array?

A Binary search is always faster because it reduces the search space by half each step, while linear search checks elements one by one.

B Linear search is faster for large arrays because it does not require sorting, unlike binary search.

C Linear search and binary search have the same cost if the target is near the start of the array.

D Binary search has a higher setup cost due to sorting, but once sorted, it is much faster than linear search for repeated searches.

💡 Hint

Consider the cost of sorting and repeated searches.

Binary search requires the array to be sorted, which can be costly initially. However, for repeated searches, binary search is much faster than linear search because it halves the search space each time.