Bit Manipulation

Welcome to the Bit Manipulation section of JDCodebase! Bit manipulation allows you to solve problems in constant time using binary logic. It’s a favorite topic in coding interviews due to its efficiency and cleverness.

What You’ll Learn

Understanding bits and binary representation
Common bitwise operators: AND, OR, XOR, NOT, shifts
Tricks for checking even/odd, swapping, counting bits
Set, unset, toggle, and check bits at specific positions
Optimizing solutions using bit masks and properties

JavaScript Bitwise Operators

a & b: Bitwise AND — 1 only if both bits are 1.

Before: 5 & 3
Code: 5 & 3; // 101 & 011 = 001
After: 1

a | b: Bitwise OR — 1 if either bit is 1.

Before: 5 | 3
Code: 5 | 3; // 101 | 011 = 111
After: 7

a ^ b: Bitwise XOR — 1 if bits are different.

Before: 5 ^ 3
Code: 5 ^ 3; // 101 ^ 011 = 110
After: 6

~a: Bitwise NOT — inverts bits (two's complement).

Before: ~5
Code: ~5; // ~00000101 = 11111010
After: -6

a << n: Left shift — multiplies by 2ⁿ.

Before: 3 << 2
Code: 3 << 2;
After: 12

a >> n: Right shift — divides by 2ⁿ (signed).

Before: 8 >> 1
Code: 8 >> 1;
After: 4

a >>> n: Unsigned right shift (zero-fill).

Before: -8 >>> 1
Code: -8 >>> 1;
After: 2147483644

Try This Example

Find the one number that appears once while all others appear twice.

function findSingleNumber(nums) {
    let result = 0;
    for (let num of nums) {
      result ^= num; // XOR cancels out duplicate values
    }
    return result;
  }

Input: [4, 1, 2, 1, 2]

Expected Output: 4