Top Array Interview Questions(2025)

Question: What is the time complexity of accessing an element in an array?

Answer:

The time complexity of accessing an element in an array is O(1), also known as constant time.

This is because arrays allow direct access to elements using an index. When you provide the index of an element, the system can immediately calculate the memory address where that element is stored (since arrays are contiguous blocks of memory), and access it in constant time, regardless of the size of the array.

Thus, no matter how large the array is, accessing an element by its index takes the same amount of time.

Question: How do you find the largest and smallest elements in an array?

Answer:

To find the largest and smallest elements in an unsorted array, you can use the following approach:

1. Initialize two variables:

   • Set one variable (max_element) to a very small value (or the first element of the array).
   • Set another variable (min_element) to a very large value (or the first element of the array).

2. Traverse the array:

   • Iterate through the array, and for each element, compare it to max_element and min_element.
   • If the current element is larger than max_element, update max_element.
   • If the current element is smaller than min_element, update min_element.

3. Return the results:

   • After iterating through the array, max_element will hold the largest element, and min_element will hold the smallest element.

Time Complexity:

• The time complexity for this approach is O(n), where n is the number of elements in the array. This is because you only need to traverse the array once to find both the largest and smallest elements.

Example in Python:

def find_max_min(arr):
## Initialize max and min with the first element
    max_element = arr[0]
    min_element = arr[0]

## Traverse the array
    for num in arr[1:]:
        if num > max_element:
            max_element = num
        if num < min_element:
            min_element = num

    return max_element, min_element

Example:

For the array [3, 1, 4, 1, 5, 9, 2, 6, 5, 3]:

• Largest element: 9
• Smallest element: 1

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