Section 1Understand Problem
Section 01
Understand the problem
Restate the problem precisely. Interviewers reward candidates who pause, define the contract, and name the guarantees before coding.
Problem statement
Given an integer array `nums`, return `true` if any value appears at least twice in the array, and `false` if every element is distinct.
Example
nums = [1, 2, 3, 1] → true
Constraints
1 ≤ nums.length ≤ 10⁵ · −10⁹ ≤ nums[i] ≤ 10⁹
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