3046. Split the Array

Description:

You are given an integer array nums of even length. You have to split the array into two parts nums1 and nums2 such that:

nums1.length == nums2.length == nums.length / 2.
nums1 should contain distinct elements.
nums2 should also contain distinct elements.
Return true if it is possible to split the array, and false otherwise.

Example 1:

Input: nums = [1,1,2,2,3,4]
Output: true
Explanation: One of the possible ways to split nums is nums1 = [1,2,3] and nums2 = [1,2,4].
Example 2:

Input: nums = [1,1,1,1]
Output: false
Explanation: The only possible way to split nums is nums1 = [1,1] and nums2 = [1,1]. Both nums1 and nums2 do not contain distinct elements. Therefore, we return false.

Thinking:

题目要求判断是否可以将数组分成两个部分，使得两个部分的元素都是不同的。
最开始考虑的是Counter()记录每个数字是否满足某个条件，如果不满足就返回False。后面发现不需要Counter，普通的字典记录，中途遇到某个数字大于2就返回False即可。

Code:

O(2n)

class Solution:
    def isPossibleToSplit(self, nums: List[int]) -> bool:
        Counter_nums = Counter(nums)
        for i, j in Counter_nums.items():
            if j > 2:
                return False
        else:
            return True

O(n)

class Solution:
    def isPossibleToSplit(self, nums: List[int]) -> bool:
        count = {}
        for num in nums:
            count[num] = count.get(num, 0) + 1
            if count[num] > 2:
                return False
        return True