217. Contains Duplicate

Question

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.

Solution

这道题很简单，用一个HashSet记录之前的数，利用HashSet的add方法，如果往set里加重复的数会返回false来判断是否有重复的数出现。

代码如下：

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

        HashSet<Integer> set = new HashSet<>();
        for (int i = 0; i < nums.length; i++) {
            if (!set.add(nums[i])) {
                return true;
            }
        }
        return false;
    }
}