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.
class Solution {
public int helper(TreeNode root, boolean take, HashMap<TreeNode, int[]> map) {
if (root == null)
return 0;
if (map.containsKey(root)) {
if (take)
return Math.max(map.get(root)[0], map.get(root)[1]);
return map.get(root)[0];
}
if (take) {
int option1 = helper(root.left, true, map) + helper(root.right, true, map);
int option2 = root.val + helper(root.left, false, map) + helper(root.right, false, map);
int[] temp = new int[] { option1, option2 };
map.put(root, temp);
return Math.max(option2, option1);
} else {
return helper(root.left, true, map) + helper(root.right, true, map);
}
}
public int rob(TreeNode root) {
HashMap<TreeNode, int[]> map = new HashMap<>();
return helper(root, true, map);
}
}