# LeetCode 268: Missing Number — Step-by-Step Visual Trace

**Easy** — Array | Bit Manipulation | Math

## The Problem

Given an array nums containing n distinct numbers in the range [0, n], find the one number that is missing from this range.

## Approach

Use XOR properties where a ^ a = 0 and a ^ 0 = a. Initialize with n, then XOR with all indices and array elements - the missing number will remain after all pairs cancel out.

**Time:** O(n) · **Space:** O(1)

## Code

```python
class Solution:
    def missingNumber(self, nums: List[int]) -> int:
        n = len(nums)
        missing_num = n

        for i in range(n):
            missing_num ^= i ^ nums[i]

        return missing_num
```

## Watch It Run

> **[Open interactive visualization](https://tracelit.dev/app?trace=0268_missing-number)**

> **Try it yourself:** Open [TraceLit](https://tracelit.dev/app?trace=0268_missing-number) and step through every line.

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