Linear Search¶

Description¶

Given an array of integers and a target value, return the index of the target if it exists in the array. Otherwise, return -1.

Linear search is the simplest search algorithm that sequentially checks each element until a match is found or the entire array has been traversed.

Approach 1: Manual Iteration¶

• Time Complexity: O(n)
• Space Complexity: O(1)

Iterate through each element in the array and check if it matches the target. Return the index when found, otherwise return -1 after the loop completes.

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

console.log(linearSearch([1, 2, 3, 4, 5], 3)); // Output: 2
console.log(linearSearch([1, 2, 3, 4, 5], 6)); // Output: -1

Approach 2: Using indexOf¶

• Time Complexity: O(n)
• Space Complexity: O(1)

JavaScript's built-in indexOf method provides a cleaner implementation. It returns the first index at which a given element can be found, or -1 if it is not present.

function linearSearch2(arr: number[], target: number): number {
  return arr.indexOf(target);
}

console.log(linearSearch2([1, 2, 3, 4, 5], 3)); // Output: 2
console.log(linearSearch2([1, 2, 3, 4, 5], 6)); // Output: -1

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