Program for decimal to hexadecimal conversion

Given a decimal number as input, we need to write a program to convert the given decimal number into an equivalent hexadecimal number. i.e. convert the number with base value 10 to base value 16.

Hexadecimal numbers use 16 values to represent a number. Numbers from 0-9 are expressed by digits 0-9 and 10-15 are represented by characters from A - F.

Examples:  

Input : 116
Output: 74

Input : 10
Output: A

Input : 33
Output: 21

Algorithm:

1. Store the remainder when the number is divided by 16 in a temporary variable temp. If the temp is less than 10, insert (48 + temp) in a character array otherwise if the temp is greater than or equal to 10, insert (55 + temp) in the character array.
2. Divide the number by 16 now
3. Repeat the above two steps until the number is not equal to 0.
4. Print the array in reverse order now.

Example

If the given decimal number is 2545. 

Step 1: Calculate the remainder when 2545 is divided by 16 is 1. Therefore, temp = 1. As temp is less than 10. So, arr[0] = 48 + 1 = 49 = '1'. 
Step 2: Divide 2545 by 16. The new number is 2545/16 = 159. 
Step 3: Calculate the remainder when 159 is divided by 16 is 15. Therefore, temp = 15. As temp is greater than 10. So, arr[1] = 55 + 15 = 70 = 'F'. 
Step 4: Divide 159 by 16. The new number is 159/16 = 9. 
Step 5: Calculate the remainder when 9 is divided by 16 is 9. Therefore, temp = 9. As temp is less than 10. So, arr[2] = 48 + 9 = 57 = '9'. 
Step 6: Divide 9 by 16. The new number is 9/16 = 0. 
Step 7: Since the number becomes = 0. Stop repeating steps and print the array in reverse order. Therefore, the equivalent hexadecimal number is 9F1.

The below diagram shows an example of converting the decimal number 2545 to an equivalent hexadecimal number.  

Below is the implementation of the above idea. 

// C++ program to convert a decimal
// number to hexadecimal number

#include <iostream>
using namespace std;

// function to convert decimal to hexadecimal
string decToHexa(int n)
{
    // ans string to store hexadecimal number
    string ans = "";
  
    while (n != 0) {
        // remainder variable to store remainder
        int rem = 0;
        
        // ch variable to store each character
        char ch;
        // storing remainder in rem variable.
        rem = n % 16;

        // check if temp < 10
        if (rem < 10) {
            ch = rem + 48;
        }
        else {
            ch = rem + 55;
        }
        
        // updating the ans string with the character variable
        ans += ch;
        n = n / 16;
    }
    
    // reversing the ans string to get the final result
    int i = 0, j = ans.size() - 1;
    while(i <= j)
    {
      swap(ans[i], ans[j]);
      i++;
      j--;
    }
    return ans;
}

// Driver code
int main()
{
    int n = 2545;

    cout << decToHexa(n);

    return 0;
}

// Java program to convert a decimal
// number to hexadecimal number
import java.io.*;

class GFG {
    // function to convert decimal to hexadecimal
    static void decToHexa(int n)
    {
        // char array to store hexadecimal number
        char[] hexaDeciNum = new char[100];

        // counter for hexadecimal number array
        int i = 0;
        while (n != 0) {
            // temporary variable to store remainder
            int temp = 0;

            // storing remainder in temp variable.
            temp = n % 16;

            // check if temp < 10
            if (temp < 10) {
                hexaDeciNum[i] = (char)(temp + 48);
                i++;
            }
            else {
                hexaDeciNum[i] = (char)(temp + 55);
                i++;
            }

            n = n / 16;
        }

        // printing hexadecimal number array in reverse
        // order
        for (int j = i - 1; j >= 0; j--)
            System.out.print(hexaDeciNum[j]);
    }

    // driver program
    public static void main(String[] args)
    {
        int n = 2545;
        decToHexa(n);
    }
}

// Contributed by Pramod Kumar

# Python3 program to
# convert a decimal
# number to hexadecimal
# number

# function to convert
# decimal to hexadecimal


def decToHexa(n):

    # char array to store
    # hexadecimal number
    hexaDeciNum = ['0'] * 100

    # counter for hexadecimal
    # number array
    i = 0
    while(n != 0):

        # temporary variable
        # to store remainder
        temp = 0

        # storing remainder
        # in temp variable.
        temp = n % 16

        # check if temp < 10
        if(temp < 10):
            hexaDeciNum[i] = chr(temp + 48)
            i = i + 1
        else:
            hexaDeciNum[i] = chr(temp + 55)
            i = i + 1
        n = int(n / 16)

    # printing hexadecimal number
    # array in reverse order
    j = i - 1
    while(j >= 0):
        print((hexaDeciNum[j]), end="")
        j = j - 1


# Driver Code
n = 2545
decToHexa(n)

# This code is contributed
# by mits.

// C# program to convert a decimal
// number to hexadecimal number
using System;

class GFG {
    // function to convert decimal
    // to hexadecimal
    static void decToHexa(int n)
    {
        // char array to store
        // hexadecimal number
        char[] hexaDeciNum = new char[100];

        // counter for hexadecimal number array
        int i = 0;
        while (n != 0) {
            // temporary variable to
            // store remainder
            int temp = 0;

            // storing remainder in temp
            // variable.
            temp = n % 16;

            // check if temp < 10
            if (temp < 10) {
                hexaDeciNum[i] = (char)(temp + 48);
                i++;
            }
            else {
                hexaDeciNum[i] = (char)(temp + 55);
                i++;
            }

            n = n / 16;
        }

        // printing hexadecimal number
        // array in reverse order
        for (int j = i - 1; j >= 0; j--)
            Console.Write(hexaDeciNum[j]);
    }

    // Driver Code
    public static void Main(String[] args)
    {
        int n = 2545;
        decToHexa(n);
    }
}

// This code is contributed by Nitin Mittal.

<script>

// Javascript program to convert a decimal
// number to hexadecimal number

// function to convert decimal to hexadecimal
function decToHexa(n)
{
    // char array to store hexadecimal number
    var hexaDeciNum = Array.from({length: 100},
                      (_, i) => 0);

    // counter for hexadecimal number array
    var i = 0;
    while (n != 0) {
        // temporary variable to store remainder
        var temp = 0;

        // storing remainder in temp variable.
        temp = n % 16;

        // check if temp < 10
        if (temp < 10) {
            hexaDeciNum[i] = 
            String.fromCharCode(temp + 48);
            i++;
        }
        else {
            hexaDeciNum[i] = 
            String.fromCharCode(temp + 55);
            i++;
        }

        n = parseInt(n / 16);
    }

    // printing hexadecimal number array in reverse
    // order
    for (j = i - 1; j >= 0; j--)
        document.write(hexaDeciNum[j]);
}

// driver program
var n = 2545;
decToHexa(n);

// This code contributed by shikhasingrajput 

</script>

<?php
// PHP program to convert 
// a decimal number to
// hexadecimal number

// function to convert 
// decimal to hexadecimal
function decToHexa($n)
{ 
    // char array to store
    // hexadecimal number
    $hexaDeciNum;
    
    // counter for hexadecimal
    // number array
    $i = 0;
    while($n != 0)
    { 
        // temporary variable
        // to store remainder
        $temp = 0;
        
        // storing remainder 
        // in temp variable.
        $temp = $n % 16;
        
        // check if temp < 10
        if($temp < 10)
        {
            $hexaDeciNum[$i] = chr($temp + 48);
            $i++;
        }
        else
        {
            $hexaDeciNum[$i] = chr($temp + 55);
            $i++;
        }
        
        $n = (int)($n / 16);
    }
    
    // printing hexadecimal number
    // array in reverse order
    for($j = $i - 1; $j >= 0; $j--)
        echo $hexaDeciNum[$j];
}

// Driver Code
$n = 2545;
decToHexa($n);

// This code is contributed 
// by mits.
?>

9F1

Time complexity: O(log₁₆n)
Auxiliary space: O(1)

Using Predefined function

// C++ program to convert decimal number to hexadecimal
#include <iostream>
using namespace std;

// function to convert decimal number to hexadecimal
void decToHexa(int n) { cout << hex << n << endl; }

// driver code
int main()
{
    int n = 2545;
    decToHexa(n);
    return 0;
}

// This code is contributed by phasing17.

// Java program to convert a decimal
// number to hexadecimal number
import java.io.*;

class GFG {
    public static void decToHexa(int n)
    {
        System.out.println(Integer.toHexString(n));
    }
    public static void main(String[] args)
    {

        int n = 2545;
        decToHexa(n);
    }
}

# function to convert decimal number
# to equivalent hexadecimal number
def decToHexa(n):
    return hex(n).replace("0x", "")

# Driver Code
n = 2545
print(decToHexa(n))

using System;

class GFG
{
    public static void decToHexa(int n)
    {
        // Convert the decimal number to hexadecimal
        Console.Write(Convert.ToString(n, 16));
    }

    public static void Main(String[] args)
    {
        int n = 2545;
        decToHexa(n);
    }
}

<script>
// JS program to convert a decimal
// number to hexadecimal number

// Function to convert decimal to hexadecimal base integer
function decToHexa(n) 
{
    document.write(n.toString(16));
}

// Driver Code
var n = 2545;
decToHexa(n);

// This code is contributed by phasing17
</script>

9f1

Time Complexity: O(log₁₆(n)), because we divide the n by 16 till it becomes zero.

Auxiliary Space: O(1), we cannot use any extra space.