Array Prototype Last

Difficulty: Easy | Acceptance: 74.70% | Paid: No Topics: N/A

Write code that enhances all arrays such that you can call the array.last() method on any array and it will return the last element. If there are no elements in the array, it should return -1.

You may assume the array is the output of JSON.parse.

• Examples
• Constraints
• Direct Index Access
• Using Array Methods

Examples

Example 1

Input:

nums = [null, {}, 3]

Output:

3

Explanation: Calling nums.last() should return the last element: 3.

Example 2

Input:

nums = []

Output:

-1

Explanation: Because there are no elements, return -1.

Constraints

0 <= arr.length <= 1000

Direct Index Access

Intuition Access the last element directly using the array’s length property to calculate the index, or return -1 if the array is empty.

Steps

• Check if the array length is 0, return -1 if true
• Return the element at index (length - 1)

class Solution:
    def last(self, arr):
        if len(arr) == 0:
            return -1
        return arr[-1]

Complexity

• Time: O(1)
• Space: O(1)
• Notes: Most efficient approach with constant time and space complexity.

Using Array Methods

Intuition Leverage built-in array methods like pop() or slice() to extract the last element, handling the empty case separately.

Steps

• Check if the array is empty, return -1 if true
• Use pop() to remove and return the last element, or slice() to get a copy of the last element

class Solution:
    def last(self, arr):
        if not arr:
            return -1
        return arr.pop()

Complexity

• Time: O(1)
• Space: O(1) for pop(), O(1) for slice(-1) as it creates a single-element array
• Notes: pop() modifies the original array, while slice() creates a copy. Direct index access is preferred for efficiency.