EASY NC#145 Blind #12 Bit Manipulation
191. Number of 1 Bits
📖 Problem
Write a function that takes the binary representation of an unsigned integer and returns the number of '1' bits it has (also known as the Hamming weight).
🧠 Visual Learning Aid
1 Model the input into the right structure
2 Choose the core technique and invariant
3 Execute step-by-step with a sample
4 Validate complexity and edge cases
JS/TS Refreshers
- •Array methods (`push`, `pop`, `shift`, `slice`)
- •Object/Map/Set usage patterns
- •Function parameter and return typing
Logical Thinking Concepts
- •Define invariants before coding
- •Check edge cases first (`[]`, single element, duplicates)
- •Estimate time/space before implementation
💡 Approach
- → Use bitwise AND with 1 to check if last bit is set
- → Right shift n to examine each bit
- → Loop until n becomes 0
- → Time: O(log n) where n is the value (max 32 iterations for 32-bit), Space: O(1)
- → in popcount
🛠️ Hints & Pitfalls
Hints
- •Use bitwise AND with 1 to check if last bit is set
- •Right shift n to examine each bit
- •Loop until n becomes 0
Common Pitfalls
- •Time: O(log n) where n is the value (max 32 iterations for 32-bit), Space: O(1)
- •in popcount
🧪 Test Cases
Hidden tests on submit: 1
Test Case 1
Not run Input:
hammingWeight(11); Expected:
3 Test Case 2
Not run Input:
hammingWeight(128); Expected:
1 Test Case 3
Not run Input:
hammingWeight(0); Expected:
0 📝 Code Editor
📤 Output