Print N to 1 Without Loop in Java

Printing numbers from N down to 1 without loop is a good exercise for understanding recursion in Java, just replace loop counter i with a parameter of the recursive function. On average, to accomplish repetitive jobs like counting down, you have to use loops.

However, recursion does the same thing by having a function call itself except with a reduced value built-in. The idea is simple: The function just prints the current number then call the same function with N−1 to 1, with the output of none when N is equal to 1.

It means that instead of the program using iterative loops to manage each call this approach uses the call stack. It offers you the understanding of the recursive process and how to solve these problems when developing your programs in Java.

Problem Overview

In other words, the aim now is to print out numbers starting from a predefined integer N down to 1That is without incorporating for, while, or do while loops. For example, if N=5, the output should be:

It can keep you from using loops in the first place, although for the beginner, this may not be easy to understand at first; recursion is an excellent method to accomplish this.

Why Use Recursion?

Recursion is a method in which a routine calls a copy of the same routine in order to solve a lesser problem. It is widely met in cases where some procedures are to be performed for several times in the task, or in general, can be represented as a sequence of sub-problems to be solved, such as factorials, Fibonacci numbers or tree problems.

Here recursive approach is permitted to generate a particular pattern of numbers, which is a descending one, in a single sequence provided the function is given to handle a particular task at a time and that is to print the number and then call itself to print the next number.

How Does Recursion Work?

Recursion: When any function is called, the details of such function are stored in the call stack - a list of active functions. After a recursive function has made its call to the next level, and hit the base case, it will stop calling the next level and the call stack starts to backtrack, every function call returns in reverse order.

File Name: PrintNumbers.java

Output:

 
Printing numbers from 5 to 1:
5
4
3
2
1   

Explanation

Recursive Method (printNTo1):

• This method takes an integer N as a parameter. It first checks if N is less than 1. If true it returns with the intent of halting further recursion.
• If N is 1 or greater it will print the current value of N.
• Then, it called it with the argument N-1 to subtract one away from the value at each iteration.

Base Case:

• The base case is when N<1. It returns when the function is in this state meaning that no further recursive is called to allow the sequence to stop.

Recursive Step:

• When N is 1 or higher the function prints N and then calls itself with N-1, to persist this sequence till N is reduced to 1.

Conclusion

In the simple problem of counting down from N to 1 without a loop, it is evident as to the power and elasticity of recursion. When recursion is discussed, the given problem may seem that it is relate only to loops but by integrating it, you will discover the basic ways of solving that particular problem.

Recursive solutions are easier and clean looking, but due to the stack problems are efficient just for tasks with not so great depth. You have also learned about the function calls and the call stack within Java, a notion you'll find relevant while doing recursive constructs in your programming, with Java or any other language.