3319 - K-th Largest Perfect Subtree Size in Binary Tree.

Medium

You are given the root of a binary tree and an integer k.

Return an integer denoting the size of the <code>k^th</code> largest perfect binary subtree, or -1 if it doesn't exist.

A perfect binary tree is a tree where all leaves are on the same level, and every parent has two children.

Example 1:

Input: root = 5,3,6,5,2,5,7,1,8,null,null,6,8, k = 2

Output: 3

Explanation:

The roots of the perfect binary subtrees are highlighted in black. Their sizes, in non-increasing order are [3, 3, 1, 1, 1, 1, 1, 1]. The <code>2^nd</code> largest size is 3.

Example 2:

Input: root = 1,2,3,4,5,6,7, k = 1

Output: 7

Explanation:

The sizes of the perfect binary subtrees in non-increasing order are [7, 3, 3, 1, 1, 1, 1]. The size of the largest perfect binary subtree is 7.

Example 3:

Input: root = 1,2,3,null,4, k = 3

Output: \-1

Explanation:

The sizes of the perfect binary subtrees in non-increasing order are [1, 1]. There are fewer than 3 perfect binary subtrees.

Constraints:

• The number of nodes in the tree is in the range [1, 2000].

• 1 <= Node.val <= 2000

• 1 <= k <= 1024