[DP] Add a solution to Regular Expression Matching

Author: soapyigu

DP/RegularExpressionMatching.swift

@@ -0,0 +1,36 @@
+/**
+ * Question Link: https://leetcode.com/problems/regular-expression-matching/
+ * Primary idea: Classic Two Dimensionel Dynamic Programming
+ * Time Complexity: O(mn), Space Complexity: O(mn)
+ */
+
+class RegularExpressionMatching {
+    func isMatch(_ s: String, _ p: String) -> Bool {
+        let sChars = Array(s), pChars = Array(p)
+        var dp = Array(repeating: Array(repeating: false, count: pChars.count + 1), count: sChars.count + 1)
+        dp[0][0] = true
+        
+        for i in 0...pChars.count {
+        	// jump over "" vs. "x*" case
+            dp[0][i] = i == 0 || i > 1 && dp[0][i - 2] && pChars[i - 1] == "*"
+        }
+        
+        for i in 0...sChars.count {
+            for j in 0...pChars.count {
+                guard j > 0 else {
+                    continue
+                }
+                
+                let pCurrent = pChars[j - 1]
+                
+                if pCurrent != "*" {
+                    dp[i][j] = i > 0 && dp[i - 1][j - 1] && (pCurrent == "." || pCurrent == sChars[i - 1])
+                } else {
+                    dp[i][j] = dp[i][j - 2] || i > 0 && j > 1 && (sChars[i - 1] == pChars[j - 2] || pChars[j - 2] == ".") && dp[i - 1][j]
+                }
+            }
+        }
+        
+        return dp[sChars.count][pChars.count]
+    }
+}

README.md

@@ -27,7 +27,7 @@
 * [Microsoft](#microsoft)
 
 ## Progress
-[Problem Status](#problem-status) shows the latest progress to all 800+ questions. Currently we have 233 completed solutions. Note: questions with ♥ mark means that you have to **Subscript to premium membership** of LeetCode to unlock them. Thank you for great contributions from [CharleneJiang](https://github.com/CharleneJiang), [ReadmeCritic](https://github.com/ReadmeCritic), [demonkoo](https://github.com/demonkoo), [DaiYue](https://github.com/DaiYue), [Quaggie](https://github.com/Quaggie) and [jindulys](https://github.com/jindulys).
+[Problem Status](#problem-status) shows the latest progress to all 800+ questions. Currently we have 234 completed solutions. Note: questions with ♥ mark means that you have to **Subscript to premium membership** of LeetCode to unlock them. Thank you for great contributions from [CharleneJiang](https://github.com/CharleneJiang), [ReadmeCritic](https://github.com/ReadmeCritic), [demonkoo](https://github.com/demonkoo), [DaiYue](https://github.com/DaiYue), [Quaggie](https://github.com/Quaggie) and [jindulys](https://github.com/jindulys).
 
 
 ## Array
@@ -194,6 +194,7 @@
 [Combination Sum IV](https://leetcode.com/problems/combination-sum-iv/)| [Swift](./DP/CombinationSumIV.swift)| Medium| O(2^n)| O(n)|
 [Triangle](https://leetcode.com/problems/triangle/)| [Swift](./DP/Triangle.swift)| Medium| O(2^n - 1)| O(m)|
 [Wildcard Matching](https://leetcode.com/problems/wildcard-matching/)| [Swift](./DP/WildcardMatching.swift)| Hard| O(mn)| O(mn)|
+[Regular Expression Matching](https://leetcode.com/problems/regular-expression-matching/)| [Swift](./DP/RegularExpressionMatching.swift)| Hard| O(mn)| O(mn)|
 [Guess Number Higher or Lower II](https://leetcode.com/problems/guess-number-higher-or-lower-ii/)| [Swift](./DP/GuessNumberHigherOrLowerII.swift)| Medium| O(nlogn)| O(n^2)|
 [Burst Ballons](https://leetcode.com/problems/burst-balloons/)| [Swift](./DP/BurstBalloons.swift)| Hard| O(n^3)| O(n)|
 [Frog Jump](https://leetcode.com/problems/frog-jump/)| [Swift](./DP/FrogJump.swift)| Hard| O(n^2)| O(n)|
@@ -741,7 +742,7 @@
 |	[Swift](./DFS/PermutationsII.swift)	|	47	|	[Permutations II](https://oj.leetcode.com/problems/permutations-ii/)	| Medium	|
 |	[Swift](./DFS/Permutations.swift)	|	46	|	[Permutations](https://oj.leetcode.com/problems/permutations/)	| Medium	|
 |		|	45	|	[Jump Game II](https://oj.leetcode.com/problems/jump-game-ii/)	| Hard	|
-|		|	44	|	[Wildcard Matching](https://oj.leetcode.com/problems/wildcard-matching/)	| Hard	|
+|	[Swift](./DP/WildcardMatching.swift)	|	44	|	[Wildcard Matching](https://oj.leetcode.com/problems/wildcard-matching/)	| Hard	|
 |	[Swift](./String/MultiplyStrings.swift)	|	43	|	[Multiply Strings](https://oj.leetcode.com/problems/multiply-strings/)	| Medium	|
 |	[Swift](./Math/TrappingRainWater.swift)	|	42	|	[Trapping Rain Water](https://oj.leetcode.com/problems/trapping-rain-water/)	| Hard	|
 |		|	41	|	[First Missing Positive](https://oj.leetcode.com/problems/first-missing-positive/)	| Hard	|
@@ -775,7 +776,7 @@
 |	[Swift](./Math/RomanToInteger.swift)	|	13	|	[Roman to Integer](https://oj.leetcode.com/problems/roman-to-integer/)	| Easy	|
 |	[Swift](./Math/IntegerToRoman.swift)	|	12	|	[Integer to Roman](https://oj.leetcode.com/problems/integer-to-roman/)	| Medium	|
 |	[Swift](./Math/ContainerMostWater.swift)	|	11	|	[Container With Most Water](https://oj.leetcode.com/problems/container-with-most-water/)	| Medium	|
-|		|	10	|	[Regular Expression Matching](https://oj.leetcode.com/problems/regular-expression-matching/)	| Hard	|
+|	[Swift](./DP/RegularExpressionMatching.swift)	|	10	|	[Regular Expression Matching](https://oj.leetcode.com/problems/regular-expression-matching/)	| Hard	|
 |	[Swift](./Math/PalindromeNumber.swift)	|	9	|	[Palindrome Number](https://oj.leetcode.com/problems/palindrome-number/)	| Easy	|
 |	[Swift](./Math/Atoi.swift)	|	8	|	[String to Integer (atoi)](https://oj.leetcode.com/problems/string-to-integer-atoi/)	| Easy	|
 |	[Swift](./Math/ReverseInteger.swift)	|	7	|	[Reverse Integer](https://oj.leetcode.com/problems/reverse-integer/)	| Easy	|