feat: add swift implementation to lcof2 problem: No.019 (#3007)

Author: klever34

lcof2/剑指 Offer II 019. 最多删除一个字符得到回文/README.md

@@ -204,6 +204,42 @@ var validPalindrome = function (s) {
 };
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    private var s: String = ""
+
+    func validPalindrome(_ s: String) -> Bool {
+        self.s = s
+        var i = s.startIndex
+        var j = s.index(before: s.endIndex)
+
+        while i < j {
+            if s[i] != s[j] {
+                return check(s.index(after: i), j) || check(i, s.index(before: j))
+            }
+            i = s.index(after: i)
+            j = s.index(before: j)
+        }
+        return true
+    }
+
+    private func check(_ i: String.Index, _ j: String.Index) -> Bool {
+        var i = i
+        var j = j
+        while i < j {
+            if s[i] != s[j] {
+                return false
+            }
+            i = s.index(after: i)
+            j = s.index(before: j)
+        }
+        return true
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof2/剑指 Offer II 019. 最多删除一个字符得到回文/Solution.swift

@@ -0,0 +1,31 @@
+class Solution {
+    private var s: String = ""
+
+    func validPalindrome(_ s: String) -> Bool {
+        self.s = s
+        var i = s.startIndex
+        var j = s.index(before: s.endIndex)
+        
+        while i < j {
+            if s[i] != s[j] {
+                return check(s.index(after: i), j) || check(i, s.index(before: j))
+            }
+            i = s.index(after: i)
+            j = s.index(before: j)
+        }
+        return true
+    }
+
+    private func check(_ i: String.Index, _ j: String.Index) -> Bool {
+        var i = i
+        var j = j
+        while i < j {
+            if s[i] != s[j] {
+                return false
+            }
+            i = s.index(after: i)
+            j = s.index(before: j)
+        }
+        return true
+    }
+}