题解 | #数组中重复的数字#

刷题打卡的第一天：

第一版：for循环的方法

class Solution:
    def duplicate(self , numbers: List[int]) -> int:
        # write code here
        for i, num1 in enumerate(numbers):
            for j, num2 in enumerate(numbers[i+1:]):
                if num2 == num1:
                    return num2
        return -1

超出运行时间，故舍弃

第二版：用result存储，再用not in 判断是否是dict的元素

class Solution:
    def duplicate(self , numbers: List[int]) -> int:
        # write code here
        result = []
        for i in range(len(numbers)):
            if numbers[i] not in result:
                result.append(numbers[i])
            else:
                return numbers[i]
        if len(result)==len(numbers):
            return -1