题解 | #数组中重复的数字#

class Solution:
    #注意类的定义
    def duplicate(self,nums):
        new_nums = set()
		#set()无序且不重复的元素集合
        for num in nums:
            if num in new_nums:
                return num
            else:
                new_nums.add(num)
        return -1