【LeetCode】337.House Robber III(Medium)解题报告

【LeetCode】337.House Robber III(Medium)解题报告

题目地址：https://leetcode.com/problems/house-robber-iii/description/
题目描述：

  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.

Solution:

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 time : O(n)
 space : O(n)
 */
class Solution {
    public int rob(TreeNode root) {
        if(root == null) return 0;
        int val = 0;
        if(root.left != null){
            val += rob(root.left.left) + rob(root.left.right);
        }
        if(root.right != null){
            val += rob(root.right.left) + rob(root.right.right);
        }
        return Math.max(val + root.val,rob(root.left)+rob(root.right));
    }
}

Date：2018年3月29日