divide-array-into-equal-pairs_2206.py

# You are given an integer array nums consisting of 2 * n integers.

# You need to divide nums into n pairs such that:

# Each element belongs to exactly one pair.
# The elements present in a pair are equal.
# Return true if nums can be divided into n pairs, otherwise return false.


# Example 1:

# Input: nums = [3,2,3,2,2,2]
# Output: true
# Explanation:
# There are 6 elements in nums, so they should be divided into 6 / 2 = 3 pairs.
# If nums is divided into the pairs (2, 2), (3, 3), and (2, 2), it will satisfy all the conditions.
# Example 2:

# Input: nums = [1,2,3,4]
# Output: false
# Explanation:
# There is no way to divide nums into 4 / 2 = 2 pairs such that the pairs satisfy every condition.


# ---------------------------------------Runtime 80 ms Beats 90.81% Memory 16.6 MB Beats 18.26%---------------------------------------


from typing import List


class Solution:
    def divideArray(self, nums: List[int]) -> bool:
        seen = set()
        for num in nums:
            if num in seen:
                seen.discard(num)
            else:
                seen.add(num)
        return not seen