Convert Hexadecimal value String to ASCII value String

Given the Hexadecimal value string as input, the task is to convert the given hexadecimal value string into its corresponding ASCII format string.

Examples: 

Input: 6765656b73
Output: geeks

Input: 6176656e67657273
Output: avengers

The “Hexadecimal” or simply “Hex” numbering system uses the Base of 16 system. Being a Base-16 system, there are 16 possible digit symbols. The hexadecimal number uses 16 symbols {0, 1, 2, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F} to represent all numbers. Here, (A, B, C, D, E, F) represents (10, 11, 12, 13, 14, 15). 

ASCII stands for American Standard Code for Information Interchange. ASCII is a standard that assigns letters, numbers, and other characters within the 256 slots available in the 8-bit code. E.g the lower case "h" character (Char) has a decimal value of 104, which is "01101000" in binary and “68” in hexadecimal. 

Algorithm:  

1. Initialize final ascii string as empty.
2. Extract first two characters from the hexadecimal string taken as input.
3. Convert it into base 16 integer.
4. Cast this integer to character which is ASCII equivalent of 2 char hex.
5. Add this character to final string.
6. Extract next two characters from hexadecimal string and go to step 3.
7. Follow these steps to extract all characters from hexadecimal string.

Implementation:

// C++ program to convert hexadecimal
// string to ASCII format string
#include <bits/stdc++.h>
using namespace std;

string hexToASCII(string hex)
{
    // initialize the ASCII code string as empty.
    string ascii = "";
    for (size_t i = 0; i < hex.length(); i += 2)
    {
        // extract two characters from hex string
        string part = hex.substr(i, 2);

        // change it into base 16 and 
        // typecast as the character
        char ch = stoul(part, nullptr, 16);

        // add this char to final ASCII string
        ascii += ch;
    }
    return ascii;
}

// Driver Code
int main()
{
    // print the ASCII string.
    cout << hexToASCII("6765656b73") << endl;

    return 0;
}

// This code is contributed by
// sanjeev2552

// Java program to convert hexadecimal
// string to ASCII format string
import java.util.Scanner;

public class HexadecimalToASCII {

    public static String hexToASCII(String hex)
    {
        // initialize the ASCII code string as empty.
        String ascii = "";

        for (int i = 0; i < hex.length(); i += 2) {

            // extract two characters from hex string
            String part = hex.substring(i, i + 2);

            // change it into base 16 and typecast as the character
            char ch = (char)Integer.parseInt(part, 16);

            // add this char to final ASCII string
            ascii = ascii + ch;
        }

        return ascii;
    }
    public static void main(String[] args)
    {
        // print the ASCII string.
        System.out.println(hexToASCII("6765656b73"));
    }
}

# Python3 program to convert hexadecimal 
# string to ASCII format string

def hexToASCII(hexx):

    # initialize the ASCII code string as empty.
    ascii = ""

    for i in range(0, len(hexx), 2):

        # extract two characters from hex string
        part = hexx[i : i + 2]

        # change it into base 16 and
        # typecast as the character 
        ch = chr(int(part, 16))

        # add this char to final ASCII string
        ascii += ch
    
    return ascii

# Driver Code
if __name__ == "__main__":

    # print the ASCII string.
    print(hexToASCII("6765656b73"))

# This code is contributed by
# sanjeev2552

// C# program to convert hexadecimal
// string to ASCII format string
using System;

class GFG 
{
    public static String hexToASCII(String hex)
    {
        // initialize the ASCII code string as empty.
        String ascii = "";

        for (int i = 0; i < hex.Length; i += 2)
        {

            // extract two characters from hex string
            String part = hex.Substring(i, 2);

            // change it into base 16 and 
            // typecast as the character
            char ch = (char)Convert.ToInt32(part, 16);;

            // add this char to final ASCII string
            ascii = ascii + ch;
        }
        return ascii;
    }
    
    // Driver Code
    public static void Main(String[] args)
    {
        // print the ASCII string.
        Console.WriteLine(hexToASCII("6765656b73"));
    }
}

// This code is contributed by PrinciRaj1992

<script>
      // JavaScript program to convert hexadecimal
      // string to ASCII format string
      function hexToASCII(hex) {
        // initialize the ASCII code string as empty.
        var ascii = "";

        for (var i = 0; i < hex.length; i += 2) {
          // extract two characters from hex string
          var part = hex.substring(i, i + 2);

          // change it into base 16 and
          // typecast as the character
          var ch = String.fromCharCode(parseInt(part, 16));

          // add this char to final ASCII string
          ascii = ascii + ch;
        }
        return ascii;
      }

      // Driver Code
      // print the ASCII string.
      document.write(hexToASCII("6765656b73"));
    </script>

geeks

Time complexity: O(N), where N is the length of the given string
Auxiliary space: O(N)

Approach 2: Using Bitwise Operations:

This approach is to use bitwise operations to directly convert the hexadecimal string to an ASCII string. In this approach, we would start by converting the hexadecimal string to a series of bytes. We can do this by iterating through the string and converting each pair of hexadecimal digits to a byte. Once we have the bytes, we can use bitwise operations to convert them to characters in the ASCII string.

In this implementation, we use a stringstream to build the ASCII string. We iterate through the hexadecimal string, converting each pair of hexadecimal digits to a byte using stoi. Then, we append the byte to the stringstream. Finally, we return the contents of the stringstream as the ASCII string.

Here is the code of this approach:

#include <bits/stdc++.h>
using namespace std;

string hexToASCII(std::string hex) {
   stringstream ss;
    for (size_t i = 0; i < hex.length(); i += 2) {
        unsigned char byte =stoi(hex.substr(i, 2), nullptr, 16);
        ss << byte;
    }
    return ss.str();
}

int main() {
    string hexString = "6765656b73";
    string asciiString = hexToASCII(hexString);
    cout << asciiString << endl;
    return 0;
}

import java.util.*;

public class HexToASCII {
    public static String hexToASCII(String hex) {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < hex.length(); i += 2) {
            String str = hex.substring(i, i + 2);
            char ch = (char) Integer.parseInt(str, 16);
            sb.append(ch);
        }
        return sb.toString();
    }

    public static void main(String[] args) {
        String hexString = "6765656b73";
        String asciiString = hexToASCII(hexString);
        System.out.println(asciiString);
    }
}

def hex_to_ascii(hex_str):
    ascii_str = ""
    for i in range(0, len(hex_str), 2):
        byte = int(hex_str[i:i+2], 16)
        ascii_str += chr(byte)
    return ascii_str

# Driver code
hex_string = "6765656b73"
ascii_string = hex_to_ascii(hex_string)
print(ascii_string)

using System;
using System.Text;

public class Program
{
    public static string HexToASCII(string hex)
    {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < hex.Length; i += 2)
        {
            byte b = Convert.ToByte(hex.Substring(i, 2), 16);
            sb.Append((char)b);
        }
        return sb.ToString();
    }

    public static void Main()
    {
        string hexString = "6765656b73";
        string asciiString = HexToASCII(hexString);
        Console.WriteLine(asciiString);
    }
}
// This code is contributed by Prajwal Kandekar

// Javascript code addition 

function hexToASCII(hex) {
  let sb = "";
  for (let i = 0; i < hex.length; i += 2) {
    let str = hex.substring(i, i + 2);
    let ch = String.fromCharCode(parseInt(str, 16));
    sb += ch;
  }
  return sb;
}

let hexString = "6765656b73";
let asciiString = hexToASCII(hexString);
console.log(asciiString);

// The code is contributed by Nidhi goel. 

Output

geeks

Time complexity: O(n), where N is the length of the given string
Auxiliary space: O(n)