217. Contains Duplicate

题目：

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.

思路：

本题思路就是建立一个哈希表，扫描一次数组，一旦发现某值再次出现就返回false。

代码：

class Solution {
public:
    bool containsDuplicate(vector<int>& nums) {
        map<int,int> mp;
        if(nums.size()<=1)
            return false;
        for(int i = 0;i<nums.size();i++)
        {
            if(mp.find(nums[i])==mp.end())
                mp[nums[i]] = nums[i];
            else 
                return true;
        }
        return false;        
    }
};