0217. Contains Duplicate

https://leetcode.com/problems/contains-duplicate

Description

Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct.

Example 1:

**Input:** nums = [1,2,3,1]
**Output:** true

Example 2:

**Input:** nums = [1,2,3,4]
**Output:** false

Example 3:

**Input:** nums = [1,1,1,3,3,4,3,2,4,2]
**Output:** true

Constraints:

• 1 <= nums.length <= 105

• -109 <= nums[i] <= 109

ac1: set

class Solution {
    public boolean containsDuplicate(int[] nums) {
        // edge case
        if (nums == null || nums.length <= 1) return false;

        Set<Integer> set = new HashSet<>();
        for (int n : nums) {
            if (set.contains(n)) return true;
            set.add(n);
        }

        return false;
    }
}

ac2: sorting

class Solution {
    public boolean containsDuplicate(int[] nums) {
        // edge case
        if (nums == null || nums.length <= 1) return false;

        Arrays.sort(nums);
        for (int i = 1; i < nums.length; i++) {
            if (nums[i] == nums[i-1]) return true;
        }

        return false;
    }
}