Given the output [3, 5] from the XOR and partition approach, and knowing the input array contains exactly two unique numbers and all others appear twice, which of the following input arrays could produce this output?

hard🔄 Reverse Engineer Q9 of Q15

Bit Manipulation - Single Number III (Two Singles)

A[1, 2, 1, 3, 2, 5]

B[3, 5, 3, 5, 1, 1]

C[3, 5, 3, 5, 2, 2]

D[1, 2, 3, 4, 5, 6]

Step-by-Step Solution

Solution:

Step 1: Check duplicates and unique elements
Output [3,5] means 3 and 5 appear once; others appear twice.
Step 2: Validate input arrays
[3, 5, 3, 5, 1, 1] has 3 and 5 once each, 1 twice; matches problem constraints.
Final Answer:
Option B -> Option B
Quick Check:
Only [3, 5, 3, 5, 1, 1] fits unique and duplicate counts [OK]

Quick Trick: Output unique numbers appear once, others twice [OK]

Common Mistakes:

MISTAKES

Choosing inputs with more than two unique numbers
Ignoring duplicate counts

Trap Explanation:

PITFALL

Candidates often pick inputs that violate problem constraints on duplicates.

Interviewer Note:

CONTEXT

Tests reverse reasoning from output to valid input arrays.

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Given the output [3, 5] from the XOR and partition approach, and knowing the input array contains exactly two unique numbers and all others appear twice, which of the following input arrays could produce this output?

Step 1: Check duplicates and unique elements

Step 2: Validate input arrays

Final Answer:

Quick Check:

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