Convert Decimal to Binary Number

The task of converting a decimal number to binary in Python involves representing the number in base-2 format, where each digit is either 0 or 1. For example, the decimal number 17 can be converted into binary, resulting in a binary representation like 10001.

Using bitwise operator

This method efficiently converts a decimal number to binary by applying bitwise operations. It continuously extracts the least significant bit using the & 1 operator and shifts the number right using >>. This is the most efficient approach in terms of performance.

n = 7  # decimal number
res = ''  # binary result
while n > 0:
    res = str(n & 1) + res
    n >>= 1
print(res)

111

Explanation: while loop extracts the least significant bit of n using n & 1, prepends it to res and right-shifts n (n >>= 1) to process the next bit, continuing until n becomes zero.

Using divide by 2

In this method, the decimal number is repeatedly divided by 2. The remainder is stored to form the binary digits. This is a straightforward and efficient way to manually convert decimal to binary, leveraging integer division.

n = 7  # decimal number
res = ''  # binary result
while n > 0:
    res = str(n % 2) + res
    n //= 2
print(res)

111

Explanation: while loop divides n by 2 (n //= 2), appending the remainder (n % 2) to res to build the binary representation. This continues until n becomes zero.

Using string concatenation method

This approach follows the same logic as the divide-by-2 method but builds the binary number by concatenating the results. While simple to understand, this method can be slower due to the overhead of string manipulation in each iteration.

n = 7  # decimal number
res = ''  # binary result
while n > 0:
    res = str(n % 2) + res
    n //= 2
print(res)

111

Explanation: In each iteration, the remainder (n % 2) is prepended to res, building the binary representation until n becomes zero.

Using recursion

Recursion method uses a divide-and-conquer approach by repeatedly dividing the decimal number by 2. The recursive function continues until the number is reduced to 1. This method is elegant but less efficient due to the function call stack.

n = 17  # decimal number
res = ''  # binary result
def dec_to_bin(n):
    if n > 1:  # recursively divide the number
        dec_to_bin(n // 2)
    global res
    res += str(n % 2)  # append the remainder (binary digit)
dec_to_bin(n)
print(res)

10001

Explanation: fun() recursively divides n by 2, appending the remainder (n % 2) to res to build the binary representation. This process continues until n is reduced to 1. Finally, the binary result stored in res is printed.

Decimal to binary in Python

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