Bit Manipulation - Find the Missing Number
Given the following code snippet, what is the output when input is [3, 0, 1]?
Given the following code snippet, what is the output when input is [3, 0, 1]?
easy🧾 Code Trace Q3 of Q15
Step-by-Step Solution
Solution:
Step 1: Trace xor_all after first loop
n=3, so i in [0,1,2,3]; xor_all = 0^1^2^3 = 0Step 2: XOR with array elements
xor_all ^= 3 -> 0^3=3; xor_all ^= 0 -> 3^0=3; xor_all ^= 1 -> 3^1=2Final Answer:
Option A -> Option AQuick Check:
Output matches missing number 2 [OK]
Quick Trick: XOR cancels pairs, leaving missing number [OK]
Common Mistakes:
MISTAKES- Off-by-one in loop range
- XOR only array or only indices
Trap Explanation:
PITFALL- Candidates often forget to XOR both indices and array elements, leading to wrong output.
Interviewer Note:
CONTEXT- Tests candidate's ability to mentally execute XOR logic on sample input.
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