Program for Decimal to Octal Conversion

11 Jul, 2022
Given a decimal number as input, we need to write a program to convert the given decimal number into an equivalent octal number. i.e convert the number with base value 10 to base value 8. The base value of a number system determines the number of digits used to represent a numeric value. For example, the binary number system uses two digits 0 and 1, the octal number system uses 8 digits from 0-7 and the decimal number system uses 10 digits 0-9 to represent any numeric value.
Examples: 
Input : 16
Output: 20

Input : 10
Output: 12

Input : 33
Output: 41
Store the remainder when the number is divided by 8 in an array.Divide the number by 8 nowRepeat the above two steps until the number is not equal to 0.Print the array in reverse order now.
Store the remainder when the number is divided by 8 in an array.
Divide the number by 8 now
Repeat the above two steps until the number is not equal to 0.
Print the array in reverse order now.
For Example: 
If the given decimal number is 16. 
Step 1: Remainder when 16 is divided by 8 is 0. Therefore, arr[0] = 0. Step 2: Divide 16 by 8. New number is 16/8 = 2. Step 3: Remainder, when 2 is divided by 8, is 2. Therefore, arr[1] = 2. Step 4: Divide 2 by 8. New number is 2/8 = 0. Step 5: Since number becomes = 0. 
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Stop repeating steps and print the array in reverse order. Therefore, the equivalent octal number is 20.
The below diagram shows an example of converting the decimal number 33 to an equivalent octal number.  
Below is the implementation of the above idea.  
C++
Java
Python3
C#
PHP
Javascript
// C++ program to convert a decimal// number to octal number #include <iostream>using namespace std; // function to convert decimal to octalvoid decToOctal(int n){     // array to store octal number    int octalNum[100];     // counter for octal number array    int i = 0;    while (n != 0) {         // storing remainder in octal array        octalNum[i] = n % 8;        n = n / 8;        i++;    }     // printing octal number array in reverse order    for (int j = i - 1; j >= 0; j--)        cout << octalNum[j];} // Driver Codeint main(){    int n = 33;     // Function Call    decToOctal(n);     return 0;}
// Java program to convert a decimal// number to octal numberimport java.io.*; class GFG {    // Function to convert decimal to octal    static void decToOctal(int n)    {        // array to store octal number        int[] octalNum = new int[100];         // counter for octal number array        int i = 0;        while (n != 0) {            // storing remainder in octal array            octalNum[i] = n % 8;            n = n / 8;            i++;        }         // Printing octal number array in reverse order        for (int j = i - 1; j >= 0; j--)            System.out.print(octalNum[j]);    }     // Driver Code    public static void main(String[] args)    {        int n = 33;         // Function Call        decToOctal(n);    }} // Contributed by Pramod Kumar
# Python3 program to convert# a decimal number to# octal number # function to convert# decimal to octal  def decToOctal(n):     # array to store    # octal number    octalNum = [0] * 100     # counter for octal    # number array    i = 0    while (n != 0):         # storing remainder        # in octal array        octalNum[i] = n % 8        n = int(n / 8)        i += 1     # printing octal number    # array in reverse order    for j in range(i - 1, -1, -1):        print(octalNum[j], end="")  # Driver Coden = 33 # Function CalldecToOctal(n) # This code is contributed# by mits
// C# program to convert a decimal// number to octal numberusing System; class GFG {     // Function to convert decimal to octal    static void decToOctal(int n)    {         // array to store octal number        int[] octalNum = new int[100];         // counter for octal number array        int i = 0;        while (n != 0) {             // storing remainder in octal array            octalNum[i] = n % 8;            n = n / 8;            i++;        }         // Printing octal number array in        // reverse order        for (int j = i - 1; j >= 0; j--)            Console.Write(octalNum[j]);    }     // Driver Code    public static void Main()    {        int n = 33;         // Function Call        decToOctal(n);    }} // This code is contributed by nitin mittal.
<?php// PHP program to convert// a decimal number to// octal number // function to convert// decimal to octalfunction decToOctal($n){         // array to store    // octal number    $octalNum;     // counter for octal    // number array    $i = 0;    while ($n != 0)    {         // storing remainder        // in octal array        $octalNum[$i] = $n % 8;        $n = (int)($n / 8);        $i++;    }     // printing octal number    // array in reverse order    for ( $j = $i - 1; $j >= 0; $j--)        echo $octalNum[$j];} // Driver Code$n = 33; // Function CalldecToOctal($n); // This code is contributed// by ajit?>
<script> // JavaScript program to convert a decimal// number to octal number // function to convert decimal to octalfunction decToOctal(n){         // array to store octal number    let octalNum = new Array(100);     // counter for octal number array    let i = 0;    while (n != 0) {         // storing remainder in octal array        octalNum[i] = n % 8;        n = Math.floor(n / 8);        i++;    }     // printing octal number array in reverse order    for (let j = i - 1; j >= 0; j--)        document.write(octalNum[j]);} // Driver Code    let n = 33;         // Function Call    decToOctal(n);  // This code is contributed by Surbhi Tyagi </script>
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Space Complexity: O(N) since creating array to store octal numbers
This problem can also be solved without using an array  using the following algorithm:
Initialize octal num to 0 and countVal to 1 and the decimal number as n
Find the remainder when decimal number divided by 8
Update octal number by octalNum + (remainder * countval)
Increase countval by countval*10
Divide decimal number by 8
Repeat from the second step until the decimal number is zero
Below is the implementation of the above idea:
C++
C
Java
Python3
C#
Javascript
// C++ program to convert decimal// number to octal number#include <iostream>using namespace std; // function to calculate the octal value of the given// decimal numbervoid decimaltoOctal(int deciNum){     // initializations    int octalNum = 0, countval = 1;    int dNo = deciNum;     while (deciNum != 0) {         // decimals remainder is calculated        int remainder = deciNum % 8;         // storing the octalvalue        octalNum += remainder * countval;         // storing exponential value        countval = countval * 10;        deciNum /= 8;    }    cout << octalNum << endl;} // Driver Codeint main(){    int n = 33;     // Function Call    decimaltoOctal(n);    return 0;}
// C program to convert decimal// number to octal number#include <stdio.h> // function to calculate the octal value of the given// decimal numbervoid decimaltoOctal(int deciNum){     int octalNum = 0, countval = 1;    int dNo = deciNum;     while (deciNum != 0) {        // decimals remainder is calculated        int remainder = deciNum % 8;         // storing the octalvalue        octalNum += remainder * countval;         // storing exponential value        countval = countval * 10;        deciNum /= 8;    }    printf("%d", octalNum);} // Driver Codeint main(){    int n = 33;     // Function Call    decimaltoOctal(n);    return 0;}
// JAVA program to convert decimal// number to octal number import java.io.*; class GFG {    // function to calculate the octal value of the given    // decimal number    static void octaltodecimal(int deciNum)    {        int octalNum = 0, countval = 1;        int dNo = deciNum;        while (deciNum != 0) {             // decimals remainder is calculated            int remainder = deciNum % 8;             // storing the octalvalue            octalNum += remainder * countval;             // storing exponential value            countval = countval * 10;            deciNum /= 8;        }        System.out.println(octalNum);    }     // Driver Code    public static void main(String[] args)    {        int n = 33;         // Function Call        octaltodecimal(n);    }}
# Python3 program to convert decimal# number to octal number # function to calculate the octal value of the given# decimal number  def decimaltoOctal(deciNum):     # initializations    octalNum = 0    countval = 1    dNo = deciNum     while (deciNum != 0):         # decimals remainder is calculated        remainder = deciNum % 8         # storing the octalvalue        octalNum += remainder * countval         # storing exponential value        countval = countval * 10        deciNum //= 8     print(octalNum)  # Driver Codeif __name__ == '__main__':     n = 33     # Function Call    decimaltoOctal(n) # This code is contributed by pratham76
// C# program to convert decimal// number to octal numberusing System;class GFG {     // function to calculate    // the octal value of the given    // decimal number    static void octaltodecimal(int deciNum)    {        int octalNum = 0, countval = 1;         while (deciNum != 0) {            // decimals remainder is            // calculated            int remainder = deciNum % 8;             // storing the octalvalue            octalNum += remainder * countval;             // storing exponential value            countval = countval * 10;            deciNum /= 8;        }        Console.Write(octalNum);    }     // Driver Code    public static void Main(string[] args)    {        int n = 33;         // Function Call        octaltodecimal(n);    }} // This code is contributed by rutvik_56
<script> // Javascript program to convert decimal// number to octal number // function to calculate the octal value of the given// decimal numberfunction decimaltoOctal(deciNum){     // initializations    let octalNum = 0, countval = 1;    let dNo = deciNum;     while (deciNum != 0) {         // decimals remainder is calculated        let remainder = Math.floor(deciNum % 8);         // storing the octalvalue        octalNum += remainder * countval;         // storing exponential value        countval = countval * 10;        deciNum = Math.floor(deciNum/8);    }    document.write(octalNum + "<br>");} // Driver Code    let n = 33;     // Function Call    decimaltoOctal(n); //This code is contributed by Mayank Tyagi </script>
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Time Complexity: O(log N)
Auxiliary Space: O(1)
Using a predefined function
Java
Python3
C#
Javascript
C++
// JAVA program to convert decimal// number to octal numberimport java.io.*; class GFG {    public static void decToOct(int n)    {        System.out.println(Integer.toOctalString(n));    }    public static void main(String[] args)    {         int n = 33;        decToOct(n);    }}
# Python program to convert decimal# number to octal number def decToOct(n):    print(oct(n)); if __name__ == '__main__':     n = 33;    decToOct(n);     # This code is contributed by Amit Katiyar
// C# program to convert decimal// number to octal numberusing System; public class GFG{    public static void decToOct(int n)    {        Console.WriteLine(Convert.ToString(n, 8));    }    public static void Main(String[] args)    {         int n = 33;        decToOct(n);    }} // This code is contributed by 29AjayKumar
<script> // Javascript program to convert decimal// number to octal numberfunction decToOct(n){    document.write(n.toString(8));}    var n = 33;decToOct(n); // This code contributed by Princi Singh </script>
#include <bits/stdc++.h>using namespace std; string intToOctal(int n){    stringstream st;    st << oct << n;    return st.str();} int main(){    int n = 43;    cout << intToOctal(n);    return 0;}
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