[Leetcode] Set

287. Find the Duplicate Number

Leetcode: https://leetcode.com/problems/find-the-duplicate-number/solution/

Solution 1. Using a set to detect duplicates

class Solution {
    public int findDuplicate(int[] nums) {
        Set<Integer> seen = new HashSet<Integer>();
        for (int num : nums) {
            if (seen.contains(num)) {
                return num;
            }
            seen.add(num);
        }

        return -1;
    }
}