217. Contains Duplicate 包含重复元素

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.

题目解析：若有重复元素，return true

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

使用HashSet，HashSet的使用方法：https://jingyan.baidu.com/article/48206aead61355216bd6b34a.html

class Solution {    public boolean containsDuplicate(int[] nums) {        if(nums.length==1 || nums.length==0) {            return false;        }        Arrays.sort(nums);        int prev = nums[0];        for(int i = 1; i < nums.length; i++) {            if(nums[i]==prev) {                return true;            }            prev = nums[i];        }        return false;    }}

这个方法是leetcode上别人先将所有元素排序，然后只需要查看相邻元素是否相同即可