Decimal to Octal in C++

We must create a software that converts a decimal number into an equal octal number given a decimal number as input i.e. convert a number having a base value of 10 to a number with a base value of 8. The number of digits used to represent a numeric value is determined by the base value of a number system.

Example of a program to convert decimal to octal in C++:

// C++ program to convert a decimal
// number to octal number
#include < iostream >
#include < bits/stdc++.h >
#include < stdlib >
using namespace std ; 
// function to convert decimal to octal
void decimalToOctal ( int n )
{
	// array to store octal number
	int octalNumber [ 100 ] ; 
	// counter for octal number array
	int i = 0 ;
	while ( n != 0 ) {
		// storing remainder in octal array
		octalNumber [ i ] = n % 8 ;
		n = n / 8 ;
		i++ ;
	}
	// printing octal number array in reverse order
	for ( int j = i - 1 ; j >= 0 ; j-- )
		cout << octalNumber [ j ] ;
}
// Driver Code
int main ( )
{
	int n = 16 ; 
	// Function Call
	decimalToOctal ( n ) ; 
	return 0;
}

OUTPUT:

20
…..
Process executed in 0.11 seconds
Press any key to continue.

Explanation:

• When 16 is divided by 8, the remainder is 0. As a result, arr [ 0 ] = 0.
• 16 divided by 8 equals 16 / 8 = 2 is the new number.
• When 2 is divided by 8, the remainder is 2. As a result, arr [ 1 ] = 2.
• 2 divided by 8, 2 / 8 = 0 is the new number.
• Since the number is equal to zero,
• Stop repeating the steps and print the array backwards. As a result, the octal number equivalent is 20.
• Time Complexity will be 0 ( logn ).

Let us see another example of a code with 0 ( 1 ) space complexity in C++:

Let us see another example of a code with 0 ( 1 ) space complexity in C++:
// C++ program to convert decimal
// number to octal number
#include < iostream >
#include < bits/stdc++.h >
#include < stdlib >
using namespace std ; 
// function to calculate the octal value of the given
// decimal number
void decimaltoOctal ( int decimalNumber )
{
	// initializations
	int octalNumber = 0 , countvalue = 1 ;
	int dNo = decimalNumber ;
	while ( decimalNumber != 0 ) {
		// decimals remainder is calculated
		int remainder = decimalNumber % 8 ; 
		// storing the octalvalue
		octalNumber += remainder * countval ; 
		// storing exponential value
		countvalue = countvalue * 10 ;
		decimalNumber /= 8 ;
	}
	cout << octalNumber << endl ;
}
// Driver Code
int main ( )
{
	int n = 16 ; 
	// Function Call
	decimaltoOctal ( n ) ;
	return 0 ;
}

OUTPUT:

20
….
Process executed in 0.11 seconds
Press any key to continue.

Explanation:

• Set the octal num to 0 and the countValue to 1, as well as the decimal number to n.
• When a decimal number is divided by 8, get the remaining.
• Updating by octalNumber + (remainder * countvalue)
• Countvalue should be multiplied by countvalue * 10.
• 8 times a decimal number
• Continue from step 2 until the decimal number reaches zero.

Let us look at another example of a program in C++ using pre defined function:

#include < bits/stdc++.h >
#include < iostream >
#include < stdlib >
using namespace std ; 
string intToOctalnum ( int n )
{
	stringstream st ;
	st << octn << n ;
	return st.str ( ) ;
}
int main ( )
{
	int n = 16 ;
	cout << intToOctalnum ( n ) ;
	return 0 ;
}

OUTPUT:

20
….
Process executed in 0.11 seconds
Press any key to continue.

Explanation:

In the above program, we have made a string function and named it as intToOctalnum and passing the decimal number as the parameter and in the main function we are making a call to function intToOctalnum.

Another example of pre defined function without using string:

#include <iostream>
using namespace std; 
long decimalToOctalnum ( long n );
int main ( ) {
    long decimalnum ;
    cout << "enter a decimal number\n";
    cin >> decimalnum;
    cout << "Octal number : " << decimalToOctalnum ( decimalnum ) ; 
    return 0;
}
long decimalToOctalnum ( long n ) {
    int remainder ; 
    long octal = 0 , i = 1 ;
   
    while ( n != 0 ) {
        remainder = n % 8 ;
        n = n / 8 ;
        octal = octal + (remainder*i);
        i = i*10;
    }
    return octal;
}

OUTPUT:

Enter a decimal number 16
Octal number: 20
………………………………………
Process executed in 0.11 seconds
Press any key to continue.

Explanation:

In the C++ program above, we accept an integer from the user and store it in the variable decimalnum. Then, using the above-mentioned procedure, we call the decimalToOctalnum function to convert the decimal function to an octal number.