217. Contains Duplicate

class Solution:
    def containsDuplicate(self, nums):
        """
        :type nums: List[int]
        :rtype: bool
        """
        result = False
        a_dict = {}
        for i in range(len(nums)):
            if nums[i] in a_dict:
                result = True
                break
            else:
                a_dict[nums[i]] = 1
        return result