solve house-robber

Author: samcho0608

house-robber/samcho0608.java

@@ -0,0 +1,29 @@
+class Solution {
+    // * can't rob two adj houses in the same night
+    // * return: max amount of money robbale in one night
+    public int rob(int[] nums) {
+        if(nums.length == 1) return nums[0];
+        if(nums.length == 2) return Math.max(nums[0], nums[1]);
+
+        // maxSum[i] = max sum possible at i (inclusive)
+        int[] maxSum = new int[nums.length];
+        maxSum[0] = nums[0];
+        maxSum[1] = nums[1];
+
+        for(int i = 2; i < nums.length; i++) {
+            if(i == 2) {
+                maxSum[i] = nums[i] + maxSum[i-2];
+                continue;
+            }
+
+            // adj houses(i-1) can't be robbed
+            // choices are:
+            // 1. i-2 th house (choosing without skipping a house)
+            // 2. i-3 th house (choosing with skipping a house)
+            //    * choosing < i-4 th houses wouldn't be optimal because it'll be missing either of 1. or 2.
+            maxSum[i] = nums[i] + Math.max(maxSum[i-2], maxSum[i-3]);
+        }
+
+        return Math.max(maxSum[nums.length-2], maxSum[nums.length-1]);
+    }
+}