掃描一遍建立哈希表，第二遍判斷哈希值。代碼如下：

class Solution(object):
    def containsDuplicate(self, nums):
        """
        :type nums: List[int]
        :rtype: bool
        """
        if len(nums) == 0 or len(nums) == 1:
            return False
        dic = {}
        for n in nums:
            if n not in dic:
                dic[n] = 1
            else:
                dic[n] += 1
        for n in nums:
            if dic[n] > 1:
                return True
        return False