Create 213. House Robber II.md

Author: TBXark

213. House Robber II.md

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+# 213. House Robber II
+
+### 2020-07-31
+
+You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed. All houses at this place are **arranged in a circle.** That means the first house is the neighbor of the last one. Meanwhile, adjacent houses have security system connected and **it will automatically contact the police if two adjacent houses were broken into on the same night**.
+
+Given a list of non-negative integers representing the amount of money of each house, determine the maximum amount of money you can rob tonight **without alerting the police**.
+
+**Example 1:**
+
+```
+Input: [2,3,2]
+Output: 3
+Explanation: You cannot rob house 1 (money = 2) and then rob house 3 (money = 2),
+             because they are adjacent houses.
+```
+
+**Example 2:**
+
+```
+Input: [1,2,3,1]
+Output: 4
+Explanation: Rob house 1 (money = 1) and then rob house 3 (money = 3).
+             Total amount you can rob = 1 + 3 = 4.
+```
+
+
+
+# Solution
+
+```swift
+
+class Solution {
+    
+    private func robLine(start: Int, end: Int, nums: [Int]) -> Int {
+        var cache = [Int: Int]()
+        for i in start..<end {
+            let x = end - i - 1 + start
+            cache[x] = max(nums[x] + (cache[x + 2] ?? 0), cache[x + 1] ?? 0)
+        }
+        return cache[start] ?? 0
+    }
+    
+    func rob(_ nums: [Int]) -> Int {
+        guard nums.count > 0 else {
+            return 0
+        }
+        if nums.count / 2 == 0 {
+            return robLine(start: 0, end: nums.count, nums: nums)
+        } else {
+            return max(robLine(start: 0, end: nums.count - 1, nums: nums), robLine(start: 1, end: nums.count, nums: nums))
+        }
+    }
+}
+
+```