TCS Coding Practice Question | Reverse a String

Last Updated : 15 Sep, 2023

Given a string, the task is to reverse this String using Command Line Arguments. Examples:

Input: Geeks
Output: skeeG

Input: GeeksForGeeks
Output: skeeGroFskeeG

Approach 1: Using another String to store the reverse

Since the string is entered as Command line Argument, there is no need for a dedicated input line
Extract the input string from the command line argument
Create a String to store the resultant reversed string, say reversedString
Traverse through this String character by character using loop, in reverse order
Now append each character into the resultant reversedString
This is the required reversed string

Program:

C

// C program to reverse a string
// using command line arguments
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
// Function to reverse the String
char* reverseString(char input[])
{
 
    // Get the length of the string
    int length = strlen(input);
    int i;
 
    // String to store the reverse
    char* reversedString
        = (char*)malloc(length * sizeof(char));
 
    // Loop through the string
    // character by character in reverse order
    // and store it into the resultant string
    for (i = length - 1; i >= 0; i--)
        reversedString[length - 1 - i] = input[i];
 
    // Return the reversed String
    return reversedString;
}
 
// Driver code
int main(int argc, char* argv[])
{
    // 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 reverse it
        printf("%s\n", reverseString(argv[1]));
    }
    return 0;
}

Java

// Java program to reverse a string
// using command line arguments
 
class GFG {
 
    // Function to reverse the String
    public static String reverseString(String input)
    {
 
        // String to store the reverse
        String reversedString = "";
 
        // Loop through the string
        // character by character in reverse order
        // and store it into the resultant string
        for (int i = input.length() - 1; i >= 0; i--)
            reversedString += input.charAt(i);
 
        // Return the reversed String
        return reversedString;
    }
 
    // 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 reverse it
            System.out.println(reverseString(args[0]));
        }
        else
            System.out.println("No command line "
                               + "arguments found.");
    }
}

Python

# Python program to reverse a string
# using command line arguments
 
import sys
 
# Function to reverse the String
def reverseString(input_str):
    # Reversing the string using slicing
    reversed_str = input_str[::-1]
    return reversed_str
 
# Driver code
if __name__ == "__main__":
    # Check if command line argument is provided
    if len(sys.argv) == 1:
        print("No command line arguments found.")
    else:
        # Get the command line argument
        # and reverse it
        print(reverseString(sys.argv[1]))

Output:

In C:
In Java:

In Python

Screenshot-2023-07-19-165133

Approach 2: Without using another String to store the reverse

Since the string is entered as Command line Argument, there is no need for a dedicated input line
Extract the input string from the command line argument
Traverse through this String character by character using loop till half the length of the string
Swap the characters from one end with the characters from the other end
This is the required reversed string

Program:

C

// C program to reverse a string
// using command line arguments
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
// Function to reverse a string
char* reverseString(char str[])
{
 
    int n = strlen(str);
    int i;
    char temp;
 
    // Swap character starting from two
    // corners
    for (i = 0; i < n / 2; i++) {
        temp = str[i];
        str[i] = str[n - i - 1];
        str[n - i - 1] = temp;
    }
 
    return str;
}
 
// Driver code
int main(int argc, char* argv[])
{
    // 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 reverse it
        reverseString(argv[1]);
 
        // Print the reversed string
        printf("%s\n", argv[1]);
    }
    return 0;
}

Java

// Java program to reverse a string
// using command line arguments
 
class GFG {
 
    // Function to reverse the String
    public static String reverseString(String str)
    {
 
        int n = str.length();
        char temp;
 
        // Swap character starting from two
        // corners
        for (int i = 0; i < n / 2; i++) {
            str = str.substring(0, i)
                  + str.charAt(n - i - 1)
                  + str.substring(i + 1, n - i - 1)
                  + str.charAt(i)
                  + str.substring(n - i);
        }
 
        return str;
    }
 
    // 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 reverse it
            System.out.println(reverseString(args[0]));
        }
        else
            System.out.println("No command line "
                               + "arguments found.");
    }
}

Output:

In C:
In Java:

TCS Coding Practice Question | Palindrome String

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