Reverse an Array - My First Data Structure Problem on HackerRank!

Problem Statement

The task was simple yet fundamental:

Given an array of integers, reverse the order of the elements and return the reversed array.

This was my first data structure problem solved on HackerRank, and it helped me understand array manipulation basics.

My Python Solution

Here is the code I wrote to solve it:

#!/bin/python3

import math
import os
import random
import re
import sys

# Complete the 'reverseArray' function below.
# The function is expected to return an INTEGER_ARRAY.
# The function accepts INTEGER_ARRAY a as parameter.

def reverseArray(a):
    # Create an empty list to store the reversed elements
    a_reverse = []
    # Iterate from the last index to the first
    for i in range(len(a) - 1, -1, -1):
        a_reverse.append(a[i])
    return a_reverse

if __name__ == '__main__':
    fptr = open(os.environ['OUTPUT_PATH'], 'w')

    arr_count = int(input().strip())
    arr = list(map(int, input().rstrip().split()))

    res = reverseArray(arr)

    fptr.write(' '.join(map(str, res)))
    fptr.write('\n')

    fptr.close()

Step-by-Step Explanation

1. Input Handling

• arr_count reads the number of elements.
• arr reads the array as a list of integers, split by spaces.

2. Logic to Reverse the Array

• I created an empty list a_reverse.
• I used a for loop to iterate from the last index to the first.
• At each iteration, I appended the element to a_reverse.
• After the loop, a_reverse contained the elements in reversed order.

3. Output Handling

• The reversed array was joined into a space-separated string and written to a file using fptr.write().

Key Python Concepts I Learned

• List traversal in reverse using range(start, stop, step) with a step of -1.
• Handling standard input and output with input() and environment-based file writing (os.environ['OUTPUT_PATH']).
• Using map() to quickly convert list elements to integers.
• Joining list elements into a single string for output.

Reflection

This problem gave me my first taste of how important array manipulation is in solving real-world problems. Even though it was simple, it laid the foundation for understanding more complex data structure operations like:

• Reversing linked lists
• Using stacks for reversal problems
• Understanding indexing and iteration patterns

I’m excited to solve more such problems and build a solid understanding of Data Structures and Algorithms (DSA)!

Final Output Example

Input:

5
1 2 3 4 5

Output:

5 4 3 2 1

Stay tuned as I continue this DSA learning journey! 🚀

“Success is the sum of small efforts, repeated day in and day out.” - Robert Collier