https://leetcode.com/problems/find-all-duplicates-in-an-array/#/description

Python (超时了）

class Solution(object):
    def findDuplicates(self, nums):
        """
        :type nums: List[int]
        :rtype: List[int]
        """
        d = dict()
        for num in nums:
            if num not in d.keys():
                d[num] = 1
            else:
                d[num] += 1
        return [k for k, v in d.items() if v == 2]

Python

• 不要用key in dict.keys() 很慢
• 用dict.has_key(key)很快

class Solution(object):
    def findDuplicates(self, nums):
        """
        :type nums: List[int]
        :rtype: List[int]
        """
        d = dict()
        re = []
        for num in nums:
            if not d.has_key(num):
                d[num] = 1
            else:
                d[num] += 1
                re.append(num)
        return re