TCS Coding Practice Question | Reverse a Number

Given a number, the task is to reverse this number using Command Line Arguments.

Examples:

Input: num = 12345
Output: 54321

Input: num = 786
Output: 687

Approach:

Since the number is entered as Command line Argument, there is no need for a dedicated input line
Extract the input number from the command line argument
This extracted number will be in String type.
Convert this number into integer type and store it in a variable, say num
Initialize a varible, say rev_num, to store the reverse of this number with 0
Now loop through the number num till it becomes 0, i.e. (num > 0)
In each iteration,
- Multiply rev_num by 10 and add remainder of num to it. This will store the last digit of num in rev_num
- Divide num by 10 to remove the last digit from it.
After the loop has ended, rev_num has the reverse of num.

Program:

C

// C program to reverse a number 
// using command line arguments 
  
#include <stdio.h> 
#include <stdlib.h>     /* atoi */ 
  
// Function to reverse the number 
int reverseNumber(int num) 
{ 
  
    // Variable to store the 
    // resultant reverse number 
    int rev_num = 0; 
  
    // Traverse through the number digit by digit 
    while (num > 0) { 
  
        // Append the last digit of num 
        // as the next digit of rev_num 
        rev_num = rev_num * 10 + num % 10; 
  
        // Remove the last digit from the num 
        num = num / 10; 
    } 
  
    // Return the reversed number 
    return rev_num; 
} 
  
// Driver code 
int main(int argc, char* argv[]) 
{ 
  
    int num; 
  
    // Check if the length of args array is 1 
    if (argc == 1) 
        printf("No command line arguments found.\n"); 
    else { 
  
        // Get the command line argument and 
        // Convert it from string type to integer type 
        // using function "atoi( argument)" 
        num = atoi(argv[1]); 
  
        // Reverse the number and print it 
        printf("%d\n", reverseNumber(num)); 
    } 
    return 0; 
} 

Java

// Java program to reverse a number 
// using command line arguments 
  
class GFG { 
  
    // Function to reverse the number 
    public static int reverseNumber(int num) 
    { 
  
        // Variable to store the 
        // resultant reverse number 
        int rev_num = 0; 
  
        // Traverse through the number digit by digit 
        while (num > 0) { 
  
            // Append the last digit of num 
            // as the next digit of rev_num 
            rev_num = rev_num * 10 + num % 10; 
  
            // Remove the last digit from the num 
            num = num / 10; 
        } 
  
        // Return the reversed number 
        return rev_num; 
    } 
  
    // Driver code 
    public static void main(String[] args) 
    { 
  
        // Check if length of args array is 
        // greater than 0 
        if (args.length > 0) { 
  
            // Get the command line argument and 
            // Convert it from string type to integer type 
            int num = Integer.parseInt(args[0]); 
  
            // Reverse the number and print it 
            System.out.println(reverseNumber(num)); 
        } 
        else
            System.out.println("No command line "
                               + "arguments found."); 
    } 
} 

Output:

In C:
In Java:

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