题目内容
The thief has found himself a new place for his thievery again. There is only one entrance to this area, called the "root." Besides the root, each house has one and only one parent house. After a tour, the smart thief realized that "all houses in this place forms a binary tree". It will automatically contact the police if two directly-linked houses were broken into on the same night.
Determine the maximum amount of money the thief can rob tonight without alerting the police.
Example 1:
Input: [3,2,3,null,3,null,1]
3
/ \
2 3
\ \
3 1
Output: 7
Explanation: Maximum amount of money the thief can rob = 3 + 3 + 1 = 7.
Example 2:
Input: [3,4,5,1,3,null,1]
3
/ \
4 5
/ \ \
1 3 1
Output: 9
Explanation: Maximum amount of money the thief can rob = 4 + 5 = 9.
题目思路
这道题目的思路在于，我们需要考虑两种可能然后根据这两种可能性进行递归。第一种，抢劫目前读取的根节点（当前节点），那么这种情况下的数值就是当前节点的数值+左右子树的子树最大数值；第二种，不抢劫当前根节点，那么这种情况下的数值就是左右两个子树的最大值。最后对于两者进行比较，取最大数值即可。