Linear Search Algorithm in DSA Javascript - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Linear Search for Existing Element

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

DSA Javascript

function linearSearch(arr, target) {
  for (let i = 0; i < arr.length; i++) {
    if (arr[i] === target) {
      return i;
    }
  }
  return -1;
}

const numbers = [3, 5, 7, 9, 11];
console.log(linearSearch(numbers, 7));

A 1

B 3

C -1

D 2

💡 Hint

Remember that array indexes start at 0 in JavaScript.

The function checks each element in order. The number 7 is at index 2 in the array, so the function returns 2.

❓ Predict Output

intermediate

Output When Element is Not Found

What does the following code print when searching for 10 in the array?

DSA Javascript

function linearSearch(arr, target) {
  for (let i = 0; i < arr.length; i++) {
    if (arr[i] === target) {
      return i;
    }
  }
  return -1;
}

const numbers = [1, 2, 3, 4, 5];
console.log(linearSearch(numbers, 10));

A -1

B 5

C 0

D undefined

💡 Hint

If the target is not in the array, what does the function return?

Since 10 is not in the array, the loop finishes without finding it, so the function returns -1.

🧠 Conceptual

advanced

Time Complexity of Linear Search

What is the worst-case time complexity of the linear search algorithm when searching in an array of size n?

A O(n log n)

B O(n)

C O(1)

D O(log n)

💡 Hint

Think about how many elements the algorithm might check in the worst case.

In the worst case, linear search checks every element once, so the time complexity is O(n).

🔧 Debug

advanced

Identify the Bug in Linear Search Implementation

What is the output of the following code when searching for 4 in the array?

DSA Javascript

function linearSearch(arr, target) {
  for (let i = 0; i <= arr.length; i++) {
    if (arr[i] === target) {
      return i;
    }
  }
  return -1;
}

const numbers = [1, 2, 3, 4, 5];
console.log(linearSearch(numbers, 4));

A TypeError: Cannot read property 'undefined' of undefined

B -1

C Returns 3

D SyntaxError

💡 Hint

Check the loop condition and array indexing carefully.

The code returns 3 because 4 is found at index 3 before the out-of-bounds access. However, the loop uses i <= arr.length, which is a bug that accesses arr[arr.length] (undefined) if the target is not found early.

🚀 Application

expert

Number of Comparisons in Linear Search

If you perform a linear search for the target value 8 in the array [2, 4, 6, 8, 10], how many comparisons does the algorithm make before finding the target?

A 4

B 3

C 5

D 2

💡 Hint

Count how many elements the algorithm checks until it finds 8.

The algorithm checks elements at indexes 0, 1, 2, and 3 before finding 8, so it makes 4 comparisons.