Check if Number is Even or Odd Using Bits in DSA Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the expression num & 1 check in a number?

It checks the least significant bit of the number. If it is 1, the number is odd; if 0, the number is even.

beginner

Why can we use bitwise AND with 1 to check if a number is even or odd?

Because the least significant bit (rightmost bit) of an odd number is always 1, and for even numbers, it is 0.

beginner

What is the output of 5 & 1 and what does it mean?

The output is 1, meaning 5 is odd.

intermediate

How does checking even or odd using bits compare to using the modulus operator?

Using bits is faster because it directly checks the binary form without division, while modulus (%) involves division.

beginner

Write a simple Python function to check if a number is even using bitwise operators.

def is_even(num): return (num & 1) == 0

What does the bitwise expression num & 1 return for an even number?

A -1

B 1

C num

D 0

For even numbers, the least significant bit is 0, so num & 1 returns 0.

Which bit of a number determines if it is even or odd?

A Most significant bit

B Second bit from right

C Least significant bit

D Middle bit

The least significant bit (rightmost bit) determines if a number is even (0) or odd (1).

What is the output of 10 & 1?

A 0

B 10

C 1

D None

10 in binary ends with 0, so 10 & 1 equals 0, meaning 10 is even.

Which operator is used to check even or odd using bits?

A Bitwise OR (|)

B Bitwise AND (&)

C Bitwise XOR (^)

D Bitwise NOT (~)

Bitwise AND (&) with 1 checks the least significant bit to determine even or odd.

Why might bitwise check for even/odd be preferred over modulus (%) in some cases?

A It is faster and uses simpler operations

B It is easier to read

C It uses less memory

D It works only for positive numbers

Bitwise operations are faster and simpler than division-based modulus operations.

Explain how to check if a number is even or odd using bitwise operators.

Think about the rightmost bit in the binary form.

Write a Python function that returns True if a number is odd using bitwise operations.

Use (num & 1) == 1 to check odd.