Java Program to Reverse a Number without using Recursion

This is the Java Program to Reverse a Given Number Without Using Recursion.

Problem Description

Write a Java Program to Reverse a Given Number Without Using Recursion.

Problem Solution

Using a loop, extract the last digit of the number and add it at the end of the reverse formed till now.
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Program/Source Code

Here is the source code of the Java Program to Reverse a Given Number Without Using Recursion. The program is successfully compiled and tested using IDE IntelliJ Idea in Windows 7. The program output is also shown below.

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//Java Program to Reverse a Given Number Without Using Recursion

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import java.io.BufferedReader;
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import java.io.InputStreamReader;
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public class ReverseNumber {
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    // Function to reverse the number without using recursion

    public static void main(String[] args) {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

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        int n;
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        try {
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            System.out.println("Enter a number");

            n = Integer.parseInt(br.readLine());

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        } catch (Exception e) {
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            System.out.println("An error occurred");

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            return;
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        }
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        int rev,i,s;
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        rev = 0;
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        for(i=n; i!=0; i/=10){
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            rev= rev*10+(i%10);
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        }
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        System.out.println("The reverse is " + rev);

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    }
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}
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Program Explanation

1. In function main(), firstly the number is taken as input.
2. Then, the loop for(i=n; i!=0; i/=10), runs until the each digit is extracted, in the reverse order.
3. The statement rev= rev*10+(i%10); adds the digit obtained to the reverse.

Time Complexity: O(1).

Runtime Test Cases

 
Case 1 (Simple Test Case):
 
Enter a number
214224
The reverse is 422412

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