#427 · #2471 · Minimum Number of Operations to Sort a Binary Tree by Level(逐层排序二叉树所需的最少操作数目)

You are given the root of a binary tree. In one operation you may swap the values of two nodes on the same level. Return the minimum number of operations to make the values sorted in non-decreasing order at every level. Constraints: the number of nodes is in [1, 10^5], 1 <= Node.val <= 10^5.