EASY NC#148 Blind #14 Bit Manipulation
268. Missing Number
📖 Problem
Given an array nums containing n distinct numbers in the range [0, n], return the only number in the range that is missing from the array.
🧠 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 XOR property: a ^ a = 0, a ^ 0 = a
- → XOR all indices 0..n with all array values
- → Duplicate numbers cancel out, leaving missing number
- → Initialize result with n, then XOR with i and nums[i]
- → Time: O(n), Space: O(1)
🛠️ Hints & Pitfalls
Hints
- •Use XOR property: a ^ a = 0, a ^ 0 = a
- •XOR all indices 0..n with all array values
- •Duplicate numbers cancel out, leaving missing number
Common Pitfalls
- •Initialize result with n, then XOR with i and nums[i]
- •Time: O(n), Space: O(1)
🧪 Test Cases
Hidden tests on submit: 1
Test Case 1
Not run Input:
missingNumber([3,0,1]); Expected:
2 Test Case 2
Not run Input:
missingNumber([0,1]); Expected:
2 Test Case 3
Not run Input:
missingNumber([9,6,4,2,3,5,7,0,1]); Expected:
8 📝 Code Editor
📤 Output