House Robber II & Type

Author: TonyKim9401

binary-tree-level-order-traversal/TonyKim9401.java

@@ -5,11 +5,11 @@
 class Solution {
     private List<List<Integer>> output = new ArrayList<>();
     public List<List<Integer>> levelOrder(TreeNode root) {
-        dsf(0, root);
+        dfs(0, root);
         return output;
     }
 
-    private void dsf(int level, TreeNode node) {
+    private void dfs(int level, TreeNode node) {
         if (node == null) return;
 
         if (output.size() == level) {
@@ -20,7 +20,7 @@ private void dsf(int level, TreeNode node) {
             output.get(level).add(node.val);
         }
         level += 1;
-        dsf(level, node.left);
-        dsf(level, node.right);
+        dfs(level, node.left);
+        dfs(level, node.right);
     }
 }

house-robber-ii/TonyKim9401.java

@@ -0,0 +1,32 @@
+// TC: O(n)
+// visit all nums at least once
+// SC: O(1)
+// only constant memory space required
+class Solution {
+    public int rob(int[] nums) {
+        if (nums.length == 1) return nums[0];
+
+        int prev = 0;
+        int post = 0;
+        int output1 = 0;
+
+        for (int i = 0; i < nums.length - 1; i++) {
+            int temp = prev;
+            prev = Math.max(post + nums[i], prev);
+            post = temp;
+        }
+        output1 = prev;
+
+        prev = 0;
+        post = 0;
+        int output2 = 0;
+        for (int i = 1; i < nums.length; i++) {
+            int temp = prev;
+            prev = Math.max(post + nums[i], prev);
+            post = temp;
+        }
+        output2 = prev;
+
+        return Math.max(output1, output2);
+    }
+}