house robber ii solution added

Author: Tessa1217

house-robber-ii/Tessa1217.java

@@ -0,0 +1,45 @@
+class Solution {
+
+    // DP
+    public int rob(int[] nums) {
+        int n = nums.length;
+
+        if (n == 0) {
+            return 0;
+        }
+
+        if (n == 1) {
+            return nums[0];
+        }
+
+        int notRobbingLast = robHouses(nums, 0, n - 2);
+        int notRobbingFirst = robHouses(nums, 1, n - 1);
+
+        return Math.max(notRobbingLast, notRobbingFirst);
+    }
+
+    private int robHouses(int[] nums, int start, int end) {
+
+        int length = end - start + 1;
+
+        if (length == 0) {
+            return 0;
+        }
+
+        if (length == 1) {
+            return nums[start];
+        }
+
+        int[] dp = new int[length];
+
+        dp[0] = nums[start];
+        dp[1] = Math.max(nums[start], nums[start + 1]);
+
+        for (int i = 2; i < length; i++) {
+            dp[i] = Math.max(dp[i - 2] + nums[start + i], dp[i - 1]);
+        }
+
+        return dp[length - 1];
+    }
+}
+