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 variable, 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 #include      /* 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);            // 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);                // Reverse the number and print it             System.out.println(reverseNumber(num));         }         else             System.out.println("No command line "                                + "arguments found.");     } }

Output:

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