Java Program to Reverse a Given Number Without Using Recursion

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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.

  1.  
  2. //Java Program to Reverse a Given Number Without Using Recursion
  3.  
  4. import java.io.BufferedReader;
  5. import java.io.InputStreamReader;
  6.  
  7. public class ReverseNumber {
  8.     // Function to reverse the number without using recursion
  9.     public static void main(String[] args) {
  10.         BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
  11.         int n;
  12.         try {
  13.             System.out.println("Enter a number");
  14.             n = Integer.parseInt(br.readLine());
  15.         } catch (Exception e) {
  16.             System.out.println("An error occurred");
  17.             return;
  18.         }
  19.         int rev,i,s;
  20.         rev = 0;
  21.         for(i=n; i!=0; i/=10){
  22.             rev= rev*10+(i%10);
  23.         }
  24.         System.out.println("The reverse is " + rev);
  25.     }
  26. }
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.

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Time Complexity: O(1).

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

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter