Leetcode No.217 存在重复元素（hash表）

class Solution(object):
    def containsDuplicate(self, nums):
        """
        :type nums: List[int]
        :rtype: bool
        """
        dict={};
        for num in nums:
            cnt=dict.get(num,0)+1;
            if cnt>=2:
                return True;
            dict[num]=cnt;
        return False;

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