217. Contains Duplicate (1)

Link

Given an array of integers, find if the array contains any duplicates.

Your function should return true if any value appears at least twice in the array, and it should return false if every element is distinct.

Example 1:

Input: [1,2,3,1]
Output: true

Example 2:

Input: [1,2,3,4]
Output: false

Example 3:

Input: [1,1,1,3,3,4,3,2,4,2]
Output: true

Solution

Use Set<Integer> to add all elements and if this one is already existed in the Set, the add operation result will be false.

class Solution {
    public boolean containsDuplicate(int[] nums) {
        Set<Integer> set = new HashSet<>(nums.length);
        for (int x: nums) {
            if(!set.add(x)){
                return true;
            }
        }
        return false;
    }
}