337.House Robber III

1 - HashMap + DFS

https://leetcode.com/problems/house-robber-iii/discuss/79330/

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public int rob(TreeNode root) {
        Map<TreeNode, Integer> map = new HashMap<>();
        return robSub(root, map);
    }

    public int robSub(TreeNode root, Map<TreeNode, Integer> map){
        if(root == null)
            return 0;
        if(map.containsKey(root))
            return map.get(root);
        int val = 0;
        if(root.left != null){
            val += robSub(root.left.left, map) + robSub(root.left.right, map);
        }
        if(root.right != null){
            val += robSub(root.right.left, map) + robSub(root.right.right, map);
        }
        val = Math.max(val + root.val, robSub(root.left, map) + robSub(root.right, map));
        map.put(root, val);
        return val;
    }
}

2 -

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public int rob(TreeNode root) {
        int[] res = robSub(root);
        return Math.max(res[0], res[1]);
    }
    public int[] robSub(TreeNode root){
        if(root == null) 
            return new int[2];
        int[] left = robSub(root.left);
        int[] right = robSub(root.right);
        int[] res = new int[2];
        res[0] = Math.max(left[0], left[1]) + Math.max(right[0], right[1]);
        res[1] = root.val + left[0] + right[0];
        return res;
    }
}