Poridhi: Basic Recursion

Basic recursion related problems:

This blog covers a series of beginner-friendly yet essential programming problems that introduce the fundamentals of function calling, recursion, iteration, and array/string manipulation using Python. It starts by explaining how general and recursive function calls work, which is crucial for understanding how code execution flows in both linear and self-referential contexts. Following that, it dives into classic number-printing problems such as printing from 1 to N, N to 1 in reverse, and from 0 to N-1, all of which build a strong foundation in loops and control structures.

The blog also addresses basic computational tasks like finding the sum or product (factorial) of the first N natural numbers—important exercises that enhance logical reasoning and mathematical thinking. Additionally, it includes common problems involving arrays and strings such as reversing an array and checking if a string is a palindrome, both of which are widely used in real-world applications. These problems are not only great practice for mastering syntax but also vital for building algorithmic thinking in any beginner programmer.

✅ How General Function Call Works

def greet(name):
    print(f"Hello, {name}!")

greet("Alice")

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✅ How Recursive Function Call Works

def recursive_hello(n):
    if n == 0:
        return
    print("Hello")
    recursive_hello(n - 1)

recursive_hello(3)

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✅ Print Number from 1 to N

def print_1_to_n(n):
    for i in range(1, n + 1):
        print(i, end=' ')

print_1_to_n(5)

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✅ Print Numbers in Reverse Order from N to 1

def print_n_to_1(n):
    for i in range(n, 0, -1):
        print(i, end=' ')

print_n_to_1(5)

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✅ Print Numbers from 0 to N-1 (Upper Bound Exclusive)

def print_0_to_n_minus_1(n):
    for i in range(n):
        print(i, end=' ')

print_0_to_n_minus_1(5)

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✅ Sum of First N Numbers

def sum_n(n):
    total = 0
    for i in range(1, n + 1):
        total += i
    return total

print(sum_n(5))  # Output: 15

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✅ Factorial / Multiplication of First N Numbers

def factorial(n):
    result = 1
    for i in range(1, n + 1):
        result *= i
    return result

print(factorial(5))  # Output: 120

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✅ Reverse an Array

def reverse_array(arr):
    return arr[::-1]

print(reverse_array([1, 2, 3, 4, 5]))

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✅ Check Palindrome String

def is_palindrome(s):
    return s == s[::-1]

print(is_palindrome("madam"))  # True
print(is_palindrome("hello"))  # False