How to do Efficient Array Traversal to Print Alternate Elements

Tutorial: Exploring Alternating Elements in an Array

In this tutorial, we’ll delve into a common programming problem where you’re given an array and tasked with printing its elements in alternate order. We’ll approach this problem step by step, ensuring a clear understanding of the solution.

Let’s dive into the problem statement:

Problem Statement: You are given an array A of size N. Your goal is to print elements of A in alternate order, starting from index 0.

Examples:

• Example 1:
  • Input:
    N = 4
    A[] = {1, 2, 3, 4}
  • Output:
    1 3
• Example 2:
  • Input:
    N = 5
    A[] = {1, 2, 3, 4, 5}
  • Output:
    1 3 5

Your Task: Since this is a function problem, you’re required to complete the provided function print(), which takes array A and its size n as input parameters and prints the resultant array in the function itself. Ensure that the final number of the array ends with a space, as the printing of newline characters is handled in the driver code.

Constraints:

• 1 ≤ N ≤ 105
• 1 ≤ Ai ≤ 105

Approach: To solve this problem efficiently, we’ll iterate through the array and print elements at even indices (0, 2, 4, …) using a loop. We’ll then traverse the array again to print elements at odd indices (1, 3, 5, …) in a similar manner.

Pseudocode:

function print(A, n):
    for i from 0 to n - 1 with step 2:
        print A[i] followed by a space
    for i from 1 to n - 1 with step 2:
        print A[i] followed by a space

Implementation (in Python):

 def print(A, n):
    for i in range(0, n, 2):
        print(A[i], end=" ")
    for i in range(1, n, 2):
        print(A[i], end=" ")

# Example usage:
A = [1, 2, 3, 4, 5]
n = len(A)
print(A, n)

Complexity Analysis:

• Time Complexity: O(n) – We iterate through the array once.
• Auxiliary Space: O(1) – We use a constant amount of extra space.

By following this approach, you can efficiently print the elements of the array in alternating order. Feel free to try implementing the solution in your preferred programming language!