"""

You are given an integer array nums and an integer k.
In one operation, you can pick two numbers from the array whose sum equals k and remove them from the array.
Return the maximum number of operations you can perform on the array.
 
Example 1:

Input: nums = [1,2,3,4], k = 5
Output: 2
Explanation: Starting with nums = [1,2,3,4]:
- Remove numbers 1 and 4, then nums = [2,3]
- Remove numbers 2 and 3, then nums = []
There are no more pairs that sum up to 5, hence a total of 2 operations.
Example 2:

Input: nums = [3,1,3,4,3], k = 6
Output: 1
Explanation: Starting with nums = [3,1,3,4,3]:
- Remove the first two 3's, then nums = [1,4,3]
There are no more pairs that sum up to 6, hence a total of 1 operation.
 
Constraints:

1 <= nums.length <= 105
1 <= nums[i] <= 109
1 <= k <= 109


"""


class Solution:
    def maxOperations(self, nums: List[int], k: int) -> int:
        c = collections.Counter(nums)
        r = 0
        for n, v in c.items():
            t = k - n
            if t not in c:
                continue
            if t == n:
                m = v // 2
                r += m
                c[n] = v - m
                continue
            m = min(v, c[t])
            r += m
            c[n] = v - m
            c[t] = c[t] - m
        return r
"""

You are given an integer array nums and an integer k.
In one operation, you can pick two numbers from the array whose sum equals k and remove them from the array.
Return the maximum number of operations you can perform on the array.
 
Example 1:

Input: nums = [1,2,3,4], k = 5
Output: 2
Explanation: Starting with nums = [1,2,3,4]:
- Remove numbers 1 and 4, then nums = [2,3]
- Remove numbers 2 and 3, then nums = []
There are no more pairs that sum up to 5, hence a total of 2 operations.
Example 2:

Input: nums = [3,1,3,4,3], k = 6
Output: 1
Explanation: Starting with nums = [3,1,3,4,3]:
- Remove the first two 3's, then nums = [1,4,3]
There are no more pairs that sum up to 6, hence a total of 1 operation.
 
Constraints:

1 <= nums.length <= 105
1 <= nums[i] <= 109
1 <= k <= 109


"""


class Solution:
    def maxOperations(self, nums: List[int], k: int) -> int:
        c = collections.Counter(nums)
        r = 0
        for n, v in c.items():
            t = k - n
            if t not in c:
                continue
            if t == n:
                m = v // 2
                r += m
                c[n] = v - m
                continue
            m = min(v, c[t])
            r += m
            c[n] = v - m
            c[t] = c[t] - m
        return r
You are given an integer array nums and an integer k. In one operation, you can pick two numbers from the array whose sum equals k and remove them from the array. Return the maximum number of operations you can perform on the array.   Example 1:  Input: nums = [1,2,3,4], k = 5 Output: 2 Explanation: Starting with nums = [1,2,3,4]: - Remove numbers 1 and 4, then nums = [2,3] - Remove numbers 2 and 3, then nums = [] There are no more pairs that sum up to 5, hence a total of 2 operations. Example 2:  Input: nums = [3,1,3,4,3], k = 6 Output: 1 Explanation: Starting with nums = [3,1,3,4,3]: - Remove the first two 3's, then nums = [1,4,3] There are no more pairs that sum up to 6, hence a total of 1 operation.   Constraints:  1 <= nums.length <= 105 1 <= nums[i] <= 109 1 <= k <= 109