leetcode217~Contains Duplicate

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.

比较简单，可以暴力求解，时间复杂度O(n^2) 也可以先排序再比较,时间复杂度O(nlogn) 使用集合，时间复杂度O(n)

public class ContainsDuplicate { public boolean containsDuplicate(int[] nums) { if(nums==null || nums.length==0) return false; Set<Integer> set = new HashSet<Integer>(); for(int i=0;i<nums.length;i++) { if(!set.add(nums[i])) { return true; } } return false; } }