Each round shows only the question description while the pattern stays hidden. Your goal is to identify the right DSA pattern by reading the wording, constraints, and clue signals.
0/0 correct
0/0 correct
0/0 correct
Difficulty affects both distractor quality and hint subtlety.
Given a list of integers, find the number that appears only once in the list. The function should take a list of integers as input and return the integer that appears only once. The list will contain at least one integer and at most 3 * 10^4 integers. Each element appears exactly twice except one. The function should return the single number in the list that appears only once.
4 clue words prepared
Hidden until you reveal this hint
Hidden until you reveal this hint
Decoding the wording makes it easier to identify the underlying structure of the pattern.
Close distractors help clear confusion, especially in cases like Sliding Window vs Prefix Sum vs Two Pointers.
After reveal, the explanation reinforces your reasoning instead of only giving the answer.
Select one pattern option based on the prompt.
Reveal hints one by one instead of spoiling the answer early.
Submit your guess and inspect the explanation.
Move to the next round without leaving the page.