小黑代码(暴力)

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def findSecondMinimumValue(self, root: Optional[TreeNode]) -> int:
        vals = set()
        def dfs(node):
            if not node:
                return 
            vals.add(node.val)
            dfs(node.left)
            dfs(node.right)
        dfs(root)
        vals = list(vals)
        if len(vals) < 2:
            return -1
        return sorted(vals)[1]

递归法

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def findSecondMinimumValue(self, root: Optional[TreeNode]) -> int:
        if not root:
            return
        self.ans, self.root_val = -1, root.val

        def dfs(node):
            # 过滤出空值 或者 值大于self.ans的
            if not node or (node.val > self.ans and self.ans != -1):
                return

            if node.val != self.root_val:
                self.ans = node.val
            dfs(node.left)
            dfs(node.right)
        dfs(root)
        return self.ans

小黑生活

看着身边的同事好卷啊，自己也要努力啊

今天早上第一次来公司科技园跑步

中午买的便当，挺便宜，两份44（午饭+晚饭），中午来个咖啡