参考代码:

class Solution:
    def secondMax(self, nums):
        maxValue = max(nums[0], nums[1])
        secValue = min(nums[0], nums[1])
        for i in range(2, len(nums)):
            if nums[i] > maxValue:
                secValue = maxValue
                maxValue = nums[i] 
            elif nums[i] > secValue:
                secValue = nums[i]
        return secValue 

参考代码:

class TreeNode:
    def __init__(self, val):
        self.val = val
        self.left, self.right = None, None


class Solution:
    def leafSum(self, root):
        p = []
        self.dfs(root, p)
        return sum(p)

    def dfs(self, root, p):
        if root is None:
            return
        if root.left is None and root.right is None:
            p.append(root.val)
        self.dfs(root.left, p)
        self.dfs(root.right, p)