217. 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.

 解题思路：

用散列是可以的，这里用set熟悉一下set的用法，可以删掉重复数据，不过复杂度会高点。set用了二叉树结构

1. class Solution {  
2. public:  
3.     bool containsDuplicate(vector<int>& nums) {  
4.         set<int> test(nums.begin(),nums.end());  
5.         if(test.size()<nums.size()) return true;  
6.         else return false;  
7.     }  
8. };