217. Existing duplicate elements C++/Python3

217. Existing duplicate elements

Thought：

For the first time**C++**Write a question
Two methods：

1. The first is sorting，Detect each time the first and the latter are equal；
2. 第二种方法是Hash table，Determine whether the number has appeared for the second time。
   existC++middle，Force buckle into the arraynumsin usevector，So it can be used directlysort()function。
   I want to usePythonmiddle的字典（Hash table）if，Give to importunordered_set<int>function新建Hash table，Re -usefind()andend()判断是否已经存exist。

Code：

SortC++

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

Hash tableC++

class Solution {
public:
    bool containsDuplicate(vector<int>& nums) {
        std::unordered_set<int> Hash;
        for(int i: nums){
            if(Hash.find(i) != Hash.end()){
                return true;
            }
            else{
                Hash.insert(i);
            }
        }
    return false;
    }
};

Hash tablepython

class Solution:
    def containsDuplicate(self, nums: List[int]) -> bool:
        dict1 = Counter(nums)
        dict1 = sorted(dict1.values())
        if dict1[-1] >= 2:
            return True
        else:
            return False