[DP] Add solutions to Paint House and Paint House II

DP/PaintHouse.swift

@@ -0,0 +1,24 @@
+/**
+ * Question Link: https://leetcode.com/problems/paint-house/
+ * Primary idea: Dynamic Programming,  dp[i][j] += min(dp[i - 1][(j + 1) % 3], dp[i - 1][(j + 2) % 3])
+ *
+ * Time Complexity: O(n), Space Complexity: O(n)
+ */
+
+class PaintHouse {
+    func minCost(_ costs: [[Int]]) -> Int {
+        guard let colors = costs.first, !colors.isEmpty else {
+            return 0
+        }
+
+        var dp = costs
+
+        for i in 1..<costs.count {
+            for j in 0..<colors.count {
+                dp[i][j] += min(dp[i - 1][(j + 1) % colors.count], dp[i - 1][(j + 2) % colors.count])
+            }
+        }
+
+        return dp[costs.count - 1].min()!
+    }
+}

DP/PaintHouseII.swift

@@ -0,0 +1,41 @@
+/**
+ * Question Link: https://leetcode.com/problems/paint-house-ii/
+ * Primary idea: Dynamic Programming, keep update previous min cost with its corresponding color
+ *               and the second min cost.
+ *
+ * Note: DP with 2-D array will throw Time Limited Error
+ * Time Complexity: O(n), Space Complexity: O(1)
+ */
+
+ class PaintHouseII {
+    func minCostII(_ costs: [[Int]]) -> Int {
+        guard let colors = costs.first, !colors.isEmpty else {
+            return 0
+        }
+
+        var preColor = -1, preMinCost = 0, preSecondMinCost = 0
+
+        for cost in costs {
+
+            var currentColor = -1, currentMinCost = Int.max, currentSecondMinCost = Int.max
+
+            for i in 0..<colors.count {
+                let sum = cost[i] + (preColor == i ? preSecondMinCost : preMinCost)
+
+                if sum < currentMinCost {
+                    currentSecondMinCost = currentMinCost
+                    currentMinCost = sum
+                    currentColor = i
+                } else if sum < currentSecondMinCost {
+                    currentSecondMinCost = sum
+                }
+            }
+
+            preColor = currentColor
+            preMinCost = currentMinCost
+            preSecondMinCost = currentSecondMinCost
+        }
+
+        return preMinCost
+    }
+}

README.md

@@ -4,7 +4,7 @@
 ![Leetcode](./logo.png?style=centerme)
 
 ## Progress
-[Problem Status](#problem-status) shows the latest progress to all 1000+ questions. Currently we have 312 completed solutions. Note: questions with ♥ mark means that you have to **Subscript to premium membership** of LeetCode to unlock them.
+[Problem Status](#problem-status) shows the latest progress to all 1000+ questions. Currently we have 314 completed solutions. Note: questions with ♥ mark means that you have to **Subscript to premium membership** of LeetCode to unlock them.
 
 ## Contributors
 
@@ -236,6 +236,8 @@
 [Maximum Sum of 3 Non-Overlapping Subarrays](https://leetcode.com/problems/maximum-sum-of-3-non-overlapping-subarrays/)| [Swift](./DP/MaximumSumThreeNonOverlappingSubarrays.swift)| Hard| O(n)| O(n)|
 [Coin Change](https://leetcode.com/problems/coin-change/)| [Swift](./DP/CoinChange.swift)| Medium| O(n^2)| O(n)|
 [Coin Change II](https://leetcode.com/problems/coin-change-ii/)| [Swift](./DP/CoinChangeII.swift)| Medium| O(n^2)| O(n)|
+[Paint House](https://leetcode.com/problems/paint-house/)| [Swift](./DP/PaintHouse.swift)| Easy| O(n)| O(n)|
+[Paint House II](https://leetcode.com/problems/paint-house-ii/)| [Swift](./DP/PaintHouseII.swift)| Hard| O(n)| O(1)|
 [Longest Increasing Subsequence](https://leetcode.com/problems/longest-increasing-subsequence/)| [Swift](./DP/LongestIncreasingSubsequence.swift)| Medium| O(nlogn)| O(n)|
 [Palindromic Substrings](https://leetcode.com/problems/palindromic-substrings/)| [Swift](./DP/PalindromicSubstrings.swift)| Medium| O(n^2)| O(n^2)|
 [Longest Palindromic Substring](https://leetcode.com/problems/longest-palindromic-substring/)| [Swift](./DP/LongestPalindromicSubstring.swift)| Medium| O(n^2)| O(n^2)|
@@ -643,15 +645,15 @@
 |	[Swift](./Math/MissingNumber.swift)	|	268	|	[Missing Number](https://leetcode.com/problems/missing-number/)	|	Easy	|
 |		|	267	|	[Palindrome Permutation II](https://leetcode.com/problems/palindrome-permutation-ii/) ♥	|	Medium	|
 |	[Swift](./String/PalindromePermutation.swift)	|	266	|	[Palindrome Permutation](https://leetcode.com/problems/palindrome-permutation/) ♥	| Easy	|
-|		|	265	|	[Paint House II](https://leetcode.com/problems/paint-house-ii/) ♥	|	Hard	|
+|	[Swift](./DP/PaintHouseII.swift)	|	265	|	[Paint House II](https://leetcode.com/problems/paint-house-ii/) ♥	|	Hard	|
 |	[Swift](./Math/UglyNumberII.swift)	|	264	|	[Ugly Number II](https://leetcode.com/problems/ugly-number-ii/)	|	Medium	|
 |	[Swift](./Math/UglyNumber.swift)	|	263	|	[Ugly Number](https://leetcode.com/problems/ugly-number/)	| Easy	|
 |	[Swift](./Sort/GraphValidTree.swift)	|	261	|	[Graph Valid Tree](https://leetcode.com/problems/graph-valid-tree/) ♥	|	Medium	|
 |		|	260	|	[Single Number III](https://leetcode.com/problems/single-number-iii/)	|	Medium	|
 |		|	259	|	[3Sum Smaller](https://leetcode.com/problems/3sum-smaller/) ♥	|	Medium	|
 |	[Swift](./Math/AddDigits.swift)	|	258	|	[Add Digits](https://leetcode.com/problems/add-digits/)	| Easy	|
 |	[Swift](./Tree/BnaryTreePaths.swift)	|	257	|	[Binary Tree Paths](https://leetcode.com/problems/binary-tree-paths/)	| Easy	|
-|		|	256	|	[Paint House](https://leetcode.com/problems/paint-house/) ♥	|	Medium	|
+|	[Swift](./DP/PaintHouse.swift)	|	256	|	[Paint House](https://leetcode.com/problems/paint-house/) ♥	|	Medium	|
 |		|	255	|	[Verify Preorder Sequence in Binary Search Tree](https://leetcode.com/problems/verify-preorder-sequence-in-binary-search-tree/) ♥	|	Medium	|
 |	[Swift](./DFS/FactorCombinations.swift)	|	254	|	[Factor Combinations](https://leetcode.com/problems/factor-combinations/) ♥	|	Medium	|
 |	[Swift](./Sort/MeetingRoomsII.swift)	|	253	|	[Meeting Rooms II](https://leetcode.com/problems/meeting-rooms-ii/) ♥	|	Medium	|