Bit Manipulation

Use bitwise operations to solve XOR, subset, and number theory problems.

8 problems 6 Easy 2 Medium 0 Hard

Overview

Bit manipulation uses bitwise AND, OR, XOR, NOT, and shifts for highly efficient solutions. XOR is particularly powerful: x ^ x = 0 and x ^ 0 = x.

When to Use

Single number (XOR trick)
Number of 1 bits (Hamming weight)
Counting bits
Reverse bits
Missing number
Sum of two integers without +

Common Mistakes

Signed vs unsigned right shift (>>> vs >>)
Operator precedence — always use parentheses
Not knowing n & (n-1) clears the lowest set bit

Complexity

Time

O(1) or O(log n) for most operations

Space

O(1)

// Common bit tricks
const getBit = (n, i) => (n >> i) & 1;
const setBit = (n, i) => n | (1 << i);
const clearBit = (n, i) => n & ~(1 << i);
const isPowerOf2 = (n) => n > 0 && (n & (n - 1)) === 0;
const lowestSetBit = (n) => n & (-n);
const clearLowestBit = (n) => n & (n - 1);

// XOR: find single number in array where all others appear twice
const singleNumber = (nums) => nums.reduce((a, b) => a ^ b, 0);

Problems (8)

Hide completed

Problem	Difficulty	Companies	Freq
Single Number	Easy	AmazonApple +1	High
Missing Number	Easy	MicrosoftAmazon	High
Counting Bits	Easy	GoogleFacebook	High
Number of 1 Bits	Easy	AppleMicrosoft +1	High
Reverse Bits	Easy	AppleAmazon	Medium
Sum of Two Integers	Medium	FacebookAmazon +1	Medium
Single Number II	Medium	AmazonFacebook	Medium
Power of Two	Easy	GoogleApple	Medium

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