1. Description
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:
3 / \ 2 3 \ \ 3 1
Maximum amount of money the thief can rob = 3 + 3 + 1 = 7.
Example 2:
3 / \ 4 5 / \ \ 1 3 1
Maximum amount of money the thief can rob = 4 + 5 = 9.
2. Answer
/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ public class Solution { public int rob(TreeNode root) { if (root == null) return 0; int first = root.val; int second = 0; if (root.left != null) { first += rob(root.left.left); first += rob(root.left.right); second += rob(root.left); } if (root.right != null) { first += rob(root.right.left); first += rob(root.right.right); second += rob(root.right); } return (first > second) ? first : second; } }
