# Program for Decimal to Binary Conversion

Last Updated : 22 Mar, 2024

Given a decimal number as input, we need to write a program to convert the given decimal number into an equivalent binary number.

### Examples of Decimal to Binary:Â

` Input : 7Output : 111Input : 10Output : 1010Input: 33Output: 100001`

## Brute force Approach

For Example:Â
If the decimal number is 10.Â
Step 1: Remainder when 10 is divided by 2 is zero. Therefore, arr[0] = 0.Â
Step 2: Divide 10 by 2. New number is 10/2 = 5.Â
Step 3: Remainder when 5 is divided by 2 is 1. Therefore, arr[1] = 1.Â
Step 4: Divide 5 by 2. New number is 5/2 = 2.Â
Step 5: Remainder when 2 is divided by 2 is zero. Therefore, arr[2] = 0.Â
Step 6: Divide 2 by 2. New number is 2/2 = 1.Â
Step 7: Remainder when 1 is divided by 2 is 1. Therefore, arr[3] = 1.Â
Step 8: Divide 1 by 2. New number is 1/2 = 0.Â
Step 9: Since number becomes = 0. Print the array in reverse order. Therefore the equivalent binary number is 1010.

The below diagram shows an example of converting the decimal number 17 to an equivalent binary number.Â

Below is the implementation of the above idea.Â Â

C++ ```// C++ program to convert a decimal // number to binary number #include <iostream> using namespace std; // function to convert decimal to binary void decToBinary(int n) { // array to store binary number int binaryNum[32]; // counter for binary array int i = 0; while (n > 0) { // storing remainder in binary array binaryNum[i] = n % 2; n = n / 2; i++; } // printing binary array in reverse order for (int j = i - 1; j >= 0; j--) cout << binaryNum[j]; } // Driver program to test above function int main() { int n = 17; decToBinary(n); return 0; } ``` C ```// C Code to convert Decimal number into Binary #include <stdio.h> void decToBinary(int n) { // array to store binary number int binaryNum[32]; // counter for binary array int i = 0; while (n > 0) { // storing remainder in binary array binaryNum[i] = n % 2; n = n / 2; i++; } // printing binary array in reverse order for (int j = i - 1; j >= 0; j--) printf("%d", binaryNum[j]); } // Driver program to test above function int main() { int n = 17; decToBinary(n); return 0; } ``` Java ```// Java program to convert a decimal // number to binary number import java.io.*; class GFG { // function to convert decimal to binary static void decToBinary(int n) { // array to store binary number int[] binaryNum = new int[32]; // counter for binary array int i = 0; while (n > 0) { // storing remainder in binary array binaryNum[i] = n % 2; n = n / 2; i++; } // printing binary array in reverse order for (int j = i - 1; j >= 0; j--) System.out.print(binaryNum[j]); } // driver program public static void main(String[] args) { int n = 17; decToBinary(n); } } // Contributed by Pramod Kumar ``` C# ```// C# program to convert a decimal // number to binary number using System; public class GFG { // function to convert decimal // to binary static void decToBinary(int n) { // array to store binary number int[] binaryNum = new int[32]; // counter for binary array int i = 0; while (n > 0) { // storing remainder in // binary array binaryNum[i] = n % 2; n = n / 2; i++; } // printing binary array // in reverse order for (int j = i - 1; j >= 0; j--) Console.Write(binaryNum[j]); } // Driver Code public static void Main() { int n = 17; decToBinary(n); } } // This code is contributed by Sam007. ``` Javascript ```<script> // Javascript program to convert a decimal // number to binary number // function to convert decimal to binary function decToBinary(n) { // array to store binary number let binaryNum = new Array(32); // counter for binary array let i = 0; while (n > 0) { // storing remainder in binary array binaryNum[i] = n % 2; n = Math.floor(n / 2); i++; } // printing binary array in reverse order for (let j = i - 1; j >= 0; j--) document.write(binaryNum[j]); } // Driver program to test above function let n = 17; decToBinary(n); // This code is contributed by Mayank Tyagi </script> ``` PHP ```<?php // PHP program to convert a decimal // number to binary number // function to convert // decimal to binary function decToBinary(\$n) { // array to store // binary number \$binaryNum; // counter for binary array \$i = 0; while (\$n > 0) { // storing remainder // in binary array \$binaryNum[\$i] = \$n % 2; \$n = (int)(\$n / 2); \$i++; } // printing binary array // in reverse order for (\$j = \$i - 1; \$j >= 0; \$j--) echo \$binaryNum[\$j]; } // Driver Code \$n = 17; decToBinary(\$n); // This code is contributed by m_kit ?> ``` Python3 ```# Python3 program to convert a # decimal number to binary number # function to convert # decimal to binary def decToBinary(n): # array to store # binary number binaryNum = [0] * n # counter for binary array i = 0; while (n > 0): # storing remainder # in binary array binaryNum[i] = n % 2 n = int(n / 2) i += 1 # printing binary array # in reverse order for j in range(i - 1, -1, -1): print(binaryNum[j], end = "") # Driver Code n = 17 decToBinary(n) # This code is contributed by mits ```

Output
```10001

```

### Time complexity: O(logn)Â & Auxiliary Space: O(1)Â

We can use bitwise operators to do the above job. Note that bitwise operators work faster than arithmetic operators used above.

C++ ```// CPP program to Decimal to binary conversion // using bitwise operator // Size of an integer is assumed to be 32 bits #include <iostream> using namespace std; // Function that convert Decimal to binary void decToBinary(int n) { // Size of an integer is assumed to be 32 bits for (int i = 31; i >= 0; i--) { int k = n >> i; if (k & 1) cout << "1"; else cout << "0"; } } // driver code int main() { int n = 32; decToBinary(n); } ``` C ```// C language to convert Decimal to binary number // using bitwise operator // Size of an integer is assumed to be 32 bits #include <stdio.h> // Function that convert Decimal to binary int decToBinary(int n) { // Size of an integer is assumed to be 32 bits for (int i = 31; i >= 0; i--) { int k = n >> i; // right shift if (k & 1) // helps us know the state of first bit printf("1"); else printf("0"); } } // driver code int main() { int n = 32; decToBinary(n); } ``` Java ```// Java program to Decimal to binary conversion // using bitwise operator // Size of an integer is assumed to be 32 bits class gfg { // Function that convert Decimal to binary public void decToBinary(int n) { // Size of an integer is assumed to be 32 bits for (int i = 31; i >= 0; i--) { int k = n >> i; if ((k & 1) > 0) System.out.print("1"); else System.out.print("0"); } } } class geek { // driver code public static void main(String[] args) { gfg g = new gfg(); int n = 32; g.decToBinary(n); } } // This code is contributed by mits ``` C# ```// C# program to Decimal to binary conversion // using bitwise operator // Size of an integer is assumed to be 32 bits using System; class gfg { // Function that convert Decimal to binary public void decToBinary(int n) { // Size of an integer is assumed to be 32 bits for (int i = 31; i >= 0; i--) { int k = n >> i; if ((k & 1) > 0) Console.Write("1"); else Console.Write("0"); } } } class geek { // driver code public static int Main() { gfg g = new gfg(); int n = 32; g.decToBinary(n); return 0; } } ``` Javascript ```<script> // javascript program to Decimal to binary conversion // using bitwise operator // Size of an integer is assumed to be 32 bits // Function that convert Decimal to binary function decToBinary(n) { // Size of an integer is assumed to be 32 bits for (i = 31; i >= 0; i--) { var k = n >> i; if ((k & 1) > 0) document.write("1"); else document.write("0"); } } // driver code var n = 32; decToBinary(n); // This code contributed by Princi Singh </script> ``` PHP ```<?php // PHP program to Decimal to binary conversion // using bitwise operator // Size of an integer is assumed // to be 32 bits // Function that convert Decimal to binary function decToBinary(\$n) { // Size of an integer is // assumed to be 32 bits for ( \$i = 31; \$i >= 0; \$i--) { \$k = \$n >> \$i; if (\$k & 1) echo "1"; else echo "0"; } } // Driver Code \$n = 32; decToBinary(\$n); // This code is contributed by aj_36 ?> ``` Python3 ```# Python3 program to Decimal # to binary conversion using # bitwise operator # Size of an integer is # assumed to be 32 bits # Function that convert # Decimal to binary def decToBinary(n): # Size of an integer is # assumed to be 32 bits for i in range(31, -1, -1): k = n >> i if (k & 1): print("1", end="") else: print("0", end="") # Driver Code n = 32 decToBinary(n) # This code is contributed by mits ```

Output
```00000000000000000000000000100000

```

### Time complexity: O(1)Â

loop iterates constant(32) number of times everytime even for small numberÂ

## Efficient Approach

It’s another efficient approach to converting Decimal to binary using the right shift(>>) and And(&) operator. Here we’ll use only Binary Operators which usually are very fast in computation.

C++ ```#include <bits/stdc++.h> using namespace std; string DecimalToBinary(int num) { string str; while(num){ if(num & 1) // 1 str+='1'; else // 0 str+='0'; num>>=1; // Right Shift by 1 } return str; } void reverse(string str) { for(int i=str.size()-1 ; i>=0 ; i--) cout<< str[i]; } int main() { int num = 59; cout<< "Binary of num 59 is: "; reverse( DecimalToBinary(num) ); return 0; } ``` Java ```// Java program to implement the // above approach import java.io.*; class GFG { // the converts decimal to binary base static String DecimalToBinary(int num) { String str = ""; while (num > 0) { if ((num & 1) == 1) // 1 str += '1'; else // 0 str += '0'; num >>= 1; // Right Shift by 1 } return str; } // reverse the string static void reverse(String str) { for (int i = str.length() - 1; i >= 0; i--) System.out.print(str.charAt(i)); } public static void main(String[] args) { int num = 59; System.out.print("Binary of num 59 is: "); reverse(DecimalToBinary(num)); } } // This code is contributed by phasing17 ``` C# ```// C# program to implement the // above approach using System; public class GFG { // this converts decimal to binary base public static string DecimalToBinary(int num) { string str = ""; while (num > 0) { if ((num & 1) == 1) // 1 str += '1'; else // 0 str += '0'; num >>= 1; // Right Shift by 1 } return str; } // reverse the string public static void reverse(String str) { for (int i = str.Length - 1; i >= 0; i--) Console.Write(str[i]); } // Driver Code public static void Main(string[] args) { int num = 59; Console.Write("Binary of num 59 is: "); reverse(DecimalToBinary(num)); } } // this code was contributed by phasing17 ``` Javascript ```<script> // JavaScript program to implement the approach // function to convert decimal to binary function DecimalToBinary(num) { var str = ""; while (num) { // adding the result of num & 1 to str if (num & 1) // 1 str += '1'; else // 0 str += '0'; // Right Shift by 1 num >>= 1; } return str; } // function to print reverse of str function reverse(str) { var res = ""; for (var i = str.length - 1; i >= 0; i--) res += (str[i]); document.write(res); } // Driver Code var num = 59; document.write("Binary of num " + num + " is: "); // function call reverse(DecimalToBinary(num)); // This code is contributed by phasing17 </script> ``` Python3 ```# Python3 program to implement the above approach # function to convert the decimal number # to binary number def DecimalToBinary(num): strs = "" while num: # if (num & 1) = 1 if (num & 1): strs += "1" # if (num & 1) = 0 else: strs += "0" # right shift by 1 num >>= 1 return strs # function to reverse the string def reverse(strs): print(strs[::-1]) # Driver Code num = 59 print("Binary of num 59 is:", end=" ") reverse(DecimalToBinary(num)) # This code is contributed by phasing17 ```

Output
```Binary of num 59 is: 111011

```

### Time Complexity: Â O(log n) & Auxiliary Space: O(1)Â

Decimal to binary conversion can also be done without using arrays.Â

C++ ```// C++ implementation of the approach #include <cmath> #include <iostream> using namespace std; #define ull unsigned long long int // Function to return the binary // equivalent of decimal value N int decimalToBinary(int N) { // To store the binary number ull B_Number = 0; int cnt = 0; while (N != 0) { int rem = N % 2; ull c = pow(10, cnt); B_Number += rem * c; N /= 2; // Count used to store exponent value cnt++; } return B_Number; } // Driver code int main() { int N = 17; cout << decimalToBinary(N); return 0; } // This code is contributed by Sania Kumari Gupta (kriSania804) ``` C ```// C implementation of the approach #include <math.h> #include <stdio.h> #define ull unsigned long long int // Function to return the binary // equivalent of decimal value N int decimalToBinary(int N) { // To store the binary number ull B_Number = 0; int cnt = 0; while (N != 0) { int rem = N % 2; ull c = pow(10, cnt); B_Number += rem * c; N /= 2; // Count used to store exponent value cnt++; } return B_Number; } // Driver code int main() { int N = 17; printf("%u", decimalToBinary(N)); return 0; } // This code is contributed by Sania Kumari Gupta (kriSania804) ``` Java ```// Java implementation of the approach import java.io.*; class GFG { // Function to return the binary // equivalent of decimal value N static int decimalToBinary(int N) { // To store the binary number int B_Number = 0; int cnt = 0; while (N != 0) { int rem = N % 2; double c = Math.pow(10, cnt); B_Number += rem * c; N /= 2; // Count used to store exponent value cnt++; } return B_Number; } // Driver code public static void main (String[] args) { int N = 17; System.out.println (decimalToBinary(N)); } } // This code is contributed by ajit. ``` C# ```// C# implementation of the approach using System; class GFG { // Function to return the binary // equivalent of decimal value N static int decimalToBinary(int N) { // To store the binary number int B_Number = 0; int cnt = 0; while (N != 0) { int rem = N % 2; int c = (int)Math.Pow(10, cnt); B_Number += rem * c; N /= 2; // Count used to store exponent value cnt++; } return B_Number; } // Driver code static public void Main () { int N = 17; Console.Write(decimalToBinary(N)); } } // This code is contributed by Tushil. ``` Javascript ```<script> // javascript implementation of the approach // Function to return the binary // equivalent of decimal value N function decimalToBinary(N) { // To store the binary number var B_Number = 0; var cnt = 0; while (N != 0) { var rem = N % 2; var c = Math.pow(10, cnt); B_Number += rem * c; N = parseInt(N/2); // Count used to store exponent value cnt++; } return B_Number; } // Driver code var N = 17; document.write(decimalToBinary(N)); // This code is contributed by Princi Singh </script> ``` Python3 ```# Python3 implementation of the approach # Function to return the binary # equivalent of decimal value N def decimalToBinary(N): # To store the binary number B_Number = 0 cnt = 0 while (N != 0): rem = N % 2 c = pow(10, cnt) B_Number += rem * c N //= 2 # Count used to store exponent value cnt += 1 return B_Number # Driver code N = 17 print(decimalToBinary(N)) # This code is contributed by # SHUBHAMSINGH10 ```

Output
```10001

```

### Time complexity: O(logn)Â & Auxiliary Space: O(1)Â

Note that this method is similar to the one where we convert Binary to Decimal as discussed in this post.
There is yet another method that converts any Decimal Number to its Binary form. The idea is to use bitset.

Below is the implementation of the above approach.Â

C++ ```//C++ program to convert a decimal number //to its binary form. //including header file #include <bits/stdc++.h> using namespace std; //Function to convert a decimal number //to its binary form string decimalToBinary(int n) { //finding the binary form of the number and //converting it to string. string s = bitset<64> (n).to_string(); //Finding the first occurrence of "1" //to strip off the leading zeroes. const auto loc1 = s.find('1'); if(loc1 != string::npos) return s.substr(loc1); return "0"; } //Driver Code int main() { int n = 17; //Function call cout << decimalToBinary(n); return 0; } //This code is contributed by yashbeersingh42 ``` Java ```// Java program to convert a decimal number to its binary // form import java.util.*; class DecimalToBinary { // Function to convert a decimal number to its binary // form public static String decimalToBinary(int n) { // Finding the binary form of the number and // converting it to a string String s = Integer.toBinaryString(n); // Finding the first occurrence of "1" to strip off // the leading zeroes int loc1 = s.indexOf("1"); if (loc1 != -1) { return s.substring(loc1); } return "0"; } // Driver code public static void main(String[] args) { int n = 17; // Function call System.out.println(decimalToBinary(n)); } } // This code is contributed by phasing17 ``` C# ```// C# program to convert a decimal number // to its binary form. using System; class HelloWorld { // Function to convert a decimal number // to its binary form public static String decimalToBinary(int n) { // finding the binary form of the number and //converting it to string. String s = Convert.ToString(n, 2); return s; } static void Main() { int n = 17; //Function call Console.WriteLine(decimalToBinary(n)); } } // The code is contributed by Nidhi goel. ``` Javascript ```// Javascript program to convert a decimal number // to its binary form. // Function to convert a decimal number // to its binary form function decimalToBinary( n) { // finding the binary form of the number and // converting it to string. const s = n.toString(2); return s; } // Driver Code let n = 17; // Function call console.log(decimalToBinary(n)); // This code is contributed by imruhrbf8. ``` Python3 ```# Python program to convert a decimal number # to its binary form. # Function to convert a decimal number # to its binary form def decimalToBinary( n): # finding the binary form of the number and # converting it to string. s = bin(n)[2:] # Finding the first occurrence of "1" # to strip off the leading zeroes. # const auto loc1 = s.find('1') loc1 = s[s.index('1'):] return loc1 return "0" # Driver Code n = 17 # Function call print(decimalToBinary(n)) ```

Output
```10001

```

## Another Approach

C++ ```// C++ program to convert Decimal to Binary Number #include <bits/stdc++.h> using namespace std; int main() { // input number int number = 15; int n = (int)(log2(number)); // binary output // using the inbuilt function cout << "the binary number is : " << bitset<64>(number).to_string().substr(64 - n - 1); } // This code is written by phasing17 ``` Java ```//To convert Decimal to Binary Number// import java.util.*; public class Main{ public static void main(String [] args){ //input// int number =15; //output// System.out.println("the binary number is : "+ Integer.toString(number,2)); //This code is written by ZEESHAN AHMAD// } } ``` C# ```// To convert Decimal to Binary Number// using System; class GFG{ public static void Main(){ // input// int number =15; //output// Console.WriteLine("the binary number is : "+ Convert.ToString(number, 2)); } } // This code is contributed by code_hunt. ``` Javascript ```// JavaScript program to convert Decimal to Binary Number // input number var number = 15; // binary output // using the inbuilt function console.log("the binary number is :", number.toString(2)); // This code is written by phasing17 ``` Python3 ```# Python3 program to convert Decimal to Binary Number # input number number = 15 # binary output # using the inbuilt function print("the binary number is :", bin(number)[2::]) # This code is written by phasing17 ```

Output
```the binary number is : 1111

```

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