leetcode-337-打家劫舍三*

题目描述：

方法一：递归

# 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 rob(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        def postorder(root):
            if root == None:
                return (0,0)
            l = postorder(root.left)
            r = postorder(root.right)
            return (root.val+l[1]+r[1] , max(l[0], l[1])+ max( r[0], r[1]))
        r = postorder(root)
        return max(r[0],r[1])

另：

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

cache = {}
def max_with_root(node):
    return node.val + max_without_root(node.left) + max_without_root(node.right) if node else 0 

def max_without_root(node):
    return helper(node.left) + helper(node.right) if node else 0 

def helper(node):
    if node in cache: return cache[node]
    cache[node] = max(max_with_root(node), max_without_root(node)) if node else 0
    return cache[node] 

class Solution(object):
    def rob(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        return helper(root)