# LeetCode 191: Number Of 1 Bits — Step-by-Step Visual Trace

**Easy** — Bit Manipulation | Math

## The Problem

Given a positive integer n, count and return the number of set bits (1s) in its binary representation.

## Approach

Use bit manipulation to check each bit position by performing bitwise AND with 1 to detect if the least significant bit is set, then right shift to examine the next bit. Continue until all bits are processed.

**Time:** O(log n) · **Space:** O(1)

## Code

```python
class Solution:
    def hammingWeight(self, n: int) -> int:
        count = 0
        while n:
            count += n & 1
            n = n >> 1
        return count
```

## Watch It Run

> **[Open interactive visualization](https://tracelit.dev/app?trace=0191_number-of-1-bits)**

> **Try it yourself:** Open [TraceLit](https://tracelit.dev/app?trace=0191_number-of-1-bits) and step through every line.

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