feat: add swift implementation to lcof problem: No.19 (doocs#2878)

Author: klever34

lcof/面试题19. 正则表达式匹配/README.md

@@ -281,6 +281,44 @@ public class Solution {
 }
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    private var memo: [[Bool?]] = []
+    private var s: [Character] = []
+    private var p: [Character] = []
+    private var m: Int = 0
+    private var n: Int = 0
+
+    func isMatch(_ s: String, _ p: String) -> Bool {
+        self.s = Array(s)
+        self.p = Array(p)
+        self.m = s.count
+        self.n = p.count
+        self.memo = Array(repeating: Array(repeating: nil, count: n + 1), count: m + 1)
+        return dfs(0, 0)
+    }
+
+    private func dfs(_ i: Int, _ j: Int) -> Bool {
+        if j >= n {
+            return i == m
+        }
+        if let res = memo[i][j] {
+            return res
+        }
+        var res = false
+        if j + 1 < n && p[j + 1] == "*" {
+            res = dfs(i, j + 2) || (i < m && (s[i] == p[j] || p[j] == ".") && dfs(i + 1, j))
+        } else {
+            res = i < m && (s[i] == p[j] || p[j] == ".") && dfs(i + 1, j + 1)
+        }
+        memo[i][j] = res
+        return res
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof/面试题19. 正则表达式匹配/Solution.swift

@@ -0,0 +1,33 @@
+class Solution {
+    private var memo: [[Bool?]] = []
+    private var s: [Character] = []
+    private var p: [Character] = []
+    private var m: Int = 0
+    private var n: Int = 0
+
+    func isMatch(_ s: String, _ p: String) -> Bool {
+        self.s = Array(s)
+        self.p = Array(p)
+        self.m = s.count
+        self.n = p.count
+        self.memo = Array(repeating: Array(repeating: nil, count: n + 1), count: m + 1)
+        return dfs(0, 0)
+    }
+
+    private func dfs(_ i: Int, _ j: Int) -> Bool {
+        if j >= n {
+            return i == m
+        }
+        if let res = memo[i][j] {
+            return res
+        }
+        var res = false
+        if j + 1 < n && p[j + 1] == "*" {
+            res = dfs(i, j + 2) || (i < m && (s[i] == p[j] || p[j] == ".") && dfs(i + 1, j))
+        } else {
+            res = i < m && (s[i] == p[j] || p[j] == ".") && dfs(i + 1, j + 1)
+        }
+        memo[i][j] = res
+        return res
+    }
+}