add solution of house-robber

Author: jinhyungrhee

house-robber/jinhyungrhee.java

@@ -0,0 +1,22 @@
+import java.util.*;
+class Solution {
+
+    // dfs with memoization => O(N)
+    public int rob(int[] nums) {
+        Map<Integer,Integer> memo = new HashMap<>();
+        return dfs(0, nums, memo);
+    }
+
+    public int dfs(int start, int[] nums, Map<Integer, Integer> memo) {
+        if (memo.containsKey(start)) return memo.get(start);
+        if (start >= nums.length) {
+            memo.put(start, 0);
+        } else {
+            memo.put(start, Math.max(
+                    nums[start] + dfs(start + 2, nums, memo),
+                    dfs(start + 1, nums, memo))
+            );
+        }
+        return memo.get(start);
+    }
+}