House Robber III
1. Title
2. My initial thoughts and problems
Slightly, look directly at the solution
3. Problem solving method one: dynamic programming method
class Solution {
Map<TreeNode, Integer> f = new HashMap<TreeNode, Integer>();
Map<TreeNode, Integer> g = new HashMap<TreeNode, Integer>();
public int rob(TreeNode root) {
dfs(root);
return Math.max(f.getOrDefault(root, 0), g.getOrDefault(root, 0));
}
public void dfs(TreeNode node) {
if (node == null) {
return;
}
dfs(node.left);
dfs(node.right);
f.put(node, node.val + g.getOrDefault(node.left, 0) + g.getOrDefault(node.right, 0));
g.put(node, Math.max(f.getOrDefault(node.left, 0), g.getOrDefault(node.left, 0)) + Math.max(f.getOrDefault(node.right, 0), g.getOrDefault(node.right, 0)));
}
}
class Solution {
public int rob(TreeNode root) {
int[] rootStatus = dfs(root);
return Math.max(rootStatus[0], rootStatus[1]);
}
public int[] dfs(TreeNode node) {
if (node == null) {
return new int[]{
0, 0};
}
int[] l = dfs(node.left);
int[] r = dfs(node.right);
int selected = node.val + l[1] + r[1];
int notSelected = Math.max(l[0], l[1]) + Math.max(r[0], r[1]);
return new int[]{
selected, notSelected};
}
}
