217. Contains Duplicate

Version #2 Sort
Version #1 HashSet

68.38 %
class Solution {
    public boolean containsDuplicate(int[] nums) {
        if (nums == null || nums.length <= 1) return false;
        Set<Integer> visited = new HashSet<>();
        for (int num : nums) {
            if (!visited.add(num)) return true;
        }
        return false;
    }
}