How to Print Numbers from 1 to N Recursively

In this tutorial, we will explore a method to print numbers from 1 to N without utilizing loops, employing recursion instead.

Understanding the Problem: The task is to print all numbers from 1 to N, where N is a given integer.

Approach: To achieve this recursively, we will define a function named printNos() that takes N as a parameter. Within this function, we will call itself recursively with the value of N decremented by 1 until N reaches 0.

Implementation Steps:

1. Define the printNos() function, which accepts an integer N as an argument.
2. Base Case: If N equals 0, the recursion terminates.
3. Recursive Step: Inside the function, print the current value of N and recursively call printNos() with N-1.

Here’s the Python code implementing this approach:

python code
def printNos(N):
    if N == 0:  # Base Case: If N equals 0, stop recursion
        return
    printNos(N - 1)  # Recursive Step: Call printNos with N-1
    print(N, end=" ")  # Print the current value of N

# Example usage:
N = 10
printNos(N)

Explanation of the Code:

• In the printNos() function, if the value of N becomes 0, the function terminates.
• Otherwise, it recursively calls itself with N-1 until the base case is reached.
• After the recursive call, it prints the current value of N.

Time and Space Complexity Analysis:

• The time complexity of this solution is O(N) because the function is called recursively N times.
• The space complexity is also O(N) due to the recursive function calls.

Conclusion: Recursion offers an elegant solution for problems like printing numbers from 1 to N without loops. By breaking down the problem into smaller subproblems, recursion allows for concise and efficient code.