题目描述

blablabla

样例

blablabla

算法1

字典 $O(n)$

class Solution(object):
    def duplicateInArray(self,nums):
        n = len(nums)
        flag = {i:0 for i in range(n)}
        ans = -1
        for _ in nums:
            if _ >= n or _ < 0:
                return -1
        for _ in nums:
            if flag[_] != 0:
                return _
            else:
                flag[_] = 1
        return -1