[Algorithm] LeetCode 217.contains-duplicate

217. Contains Duplicate

Easy

---

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

 

solution:

class Solution {
    public boolean containsDuplicate(int[] nums) {
        HashSet<Integer> numsHash = new HashSet<>();
        
        for (int i = 0; i < nums.length; i++) {
            numsHash.add(nums[i]);
            if (numsHash.size() != i + 1) return true;
        }
        
        return false;
    }
}