CodeSignal Technical Assessment Bit Manipulation and Mathematical Reasoning 2

Question 1

To find the single non-repeating element in an array where every other element appears exactly twice, which operation is applied across all elements?

Accepted Answer

XOR all elements

Answer

XOR of any number with itself is 0, so paired elements cancel out and the unique element remains.

Question 2

What is the GCD of 48 and 18?

Accepted Answer

6

Answer

Applying the Euclidean algorithm: gcd(48,18)=gcd(18,12)=gcd(12,6)=gcd(6,0)=6.

Question 3

How many set bits does the number 12 (binary 1100) have?

Accepted Answer

2

Answer

12 in binary is 1100, which has exactly two 1-bits.

Question 4

What is `~0` in a 32-bit two's complement integer system?

Accepted Answer

-1

Answer

Bitwise NOT of 0 flips all 32 bits to 1, which represents -1 in two's complement encoding.

Question 5

What is (7 × 8) mod 5?

Accepted Answer

1

Answer

7 × 8 = 56, and 56 mod 5 = 1 because 56 = 11 × 5 + 1.

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