[Solved] Consider the following code to find the missing number in an array containing numbers from 0 to n with... What is the value of xor_all just before the return statement when the input is [3, 0, 1]? | Bit Manipulation

Bit Manipulation - Find the Missing Number

Consider the following code to find the missing number in an array containing numbers from 0 to n with one missing. What is the value of xor_all just before the return statement when the input is [3, 0, 1]?

A2

B3

C0

D1

Step-by-Step Solution

Step 1: Trace xor_all after first loop (XOR 0 to 3)
0 ^ 0 = 0, 0 ^ 1 = 1, 1 ^ 2 = 3, 3 ^ 3 = 0
Step 2: XOR xor_all with each array element
0 ^ 3 = 3, 3 ^ 0 = 3, 3 ^ 1 = 2
Final Answer:
Option A -> Option A
Quick Check:
Final xor_all is 2, the missing number [OK]

Quick Trick: XOR all indices and elements cancels pairs leaving missing number [OK]

Common Mistakes:

MISTAKES

Off-by-one in range causing wrong xor_all
XORing only array or only indices
Misreading xor_all updates

Trap Explanation:

PITFALL

Candidates often forget that XORing 0 to n includes n, or confuse order of XOR operations.

Interviewer Note:

CONTEXT

Tests candidate's ability to mentally execute XOR logic and boundary conditions

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More Bit Manipulation Quizzes

What is the value of xor_all just before the return statement when the input is [3, 0, 1]?

Step 1: Trace xor_all after first loop (XOR 0 to 3)

Step 2: XOR xor_all with each array element

Final Answer:

Quick Check:

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