技術標籤：演算法

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def kthLargest(self, root, k):
        """
        :type root: TreeNode
        :type k: int
        :rtype: int
        """
        def dfs(root):
            if not root: 
                return
            dfs(root.right)
            if self.k == 0: 
                return
            self.k -= 1
            if self.k == 0: 
                self.res = root.val
            dfs(root.left)

        self.k = k
        dfs(root)
        return self.res