Here’s a comprehensive list of Bit Manipulation Techniques and Interview Practice Problems with related LeetCode/GeeksforGeeks questions where possible.

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1. Basics of Bit Manipulation

Understanding the core bitwise operators is essential for solving bit manipulation problems.

• AND (&): Masks bits, used to clear bits or check specific bits.
• OR (|): Sets specific bits in a number.
• XOR (^): Flips bits when two bits are different, used for toggling bits or checking equality.
• NOT (~): Inverts all bits.
• Left Shift (<<): Multiplies by powers of two.
• Right Shift (>>): Divides by powers of two.
• Key Concept: Understanding how these operators work on binary representations of numbers.

Example Questions:

1. LeetCode #191 - Number of 1 Bits
2. LeetCode #231 - Power of Two
3. LeetCode #371 - Sum of Two Integers
4. GeeksforGeeks - Count set bits
5. LeetCode #136 - Single Number
6. GeeksforGeeks - Check whether K-th bit is set or not
7. LeetCode #268 - Missing Number
8. GeeksforGeeks - Check if a number is odd or even
9. LeetCode #190 - Reverse Bits
10. GeeksforGeeks - Toggle K-th bit

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2. Power of Two Checks

• Approach: To check if a number n is a power of two, use n & (n - 1). If the result is 0, it’s a power of two.

Key Insight: Powers of two have only one bit set in their binary representation.

Example Questions:

1. LeetCode #231 - Power of Two
2. GeeksforGeeks - Check if a number is a power of two
3. LeetCode #342 - Power of Four
4. LeetCode #326 - Power of Three
5. LeetCode #693 - Binary Number with Alternating Bits
6. LeetCode #137 - Single Number II
7. GeeksforGeeks - Count total set bits in all numbers from 1 to N
8. LeetCode #338 - Counting Bits
9. GeeksforGeeks - Turn off the rightmost set bit
10. GeeksforGeeks - Position of rightmost set bit

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3. Counting Set Bits

• Approach: Use x &= (x - 1) to remove the lowest set bit and keep counting until x == 0. This helps count the number of 1’s (set bits) in the binary representation.

Key Insight: Each x &= (x - 1) removes the lowest set bit, making it ideal for counting bits.

Example Questions:

1. LeetCode #191 - Number of 1 Bits
2. GeeksforGeeks - Brian Kernighan’s Algorithm
3. LeetCode #338 - Counting Bits
4. GeeksforGeeks - Flip all bits of a number
5. LeetCode #476 - Number Complement
6. GeeksforGeeks - Swap all odd and even bits
7. LeetCode #89 - Gray Code
8. GeeksforGeeks - Find parity of a number
9. LeetCode #67 - Add Binary
10. LeetCode #405 - Convert a Number to Hexadecimal

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4. Swapping Numbers Using XOR

• Approach: You can swap two numbers x and y without using a temporary variable with the following operations:
  1. x = x ^ y
  2. y = x ^ y
  3. x = x ^ y

Key Insight: XORing a number with itself results in 0, so swapping can be done in-place without using additional space.

Example Questions:

1. LeetCode #136 - Single Number
2. GeeksforGeeks - Swap two numbers without a temporary variable
3. LeetCode #137 - Single Number II
4. GeeksforGeeks - Swap all odd and even bits
5. LeetCode #260 - Single Number III
6. LeetCode #645 - Set Mismatch
7. GeeksforGeeks - Find the only odd occurring element
8. LeetCode #260 - Single Number III
9. LeetCode #137 - Single Number II
10. LeetCode #268 - Missing Number

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5. Reversing Bits

• Approach: Reversing the bits of a number involves extracting each bit and shifting it into its reverse position.

Key Insight: By shifting bits one at a time and using bitwise OR, you can reverse the order of bits in a number.

Example Questions:

1. LeetCode #190 - Reverse Bits
2. GeeksforGeeks - Reverse bits of a number
3. LeetCode #405 - Convert a Number to Hexadecimal
4. LeetCode #190 - Reverse Bits
5. GeeksforGeeks - Find whether a number is a palindrome in binary representation
6. LeetCode #1290 - Convert Binary Number in a Linked List to Integer
7. GeeksforGeeks - Reverse individual bits of a number
8. LeetCode #405 - Convert a Number to Hexadecimal
9. GeeksforGeeks - Reverse a linked list using bitwise operators
10. GeeksforGeeks - Convert Binary to Gray code

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This list provides a comprehensive guide to mastering bit manipulation, with more than 10 examples in each section for targeted practice on LeetCode and GeeksforGeeks.