feat: add swift implementation to lcof problem: No.12 (doocs#2864)

Author: klever34

lcof/面试题12. 矩阵中的路径/README.md

@@ -366,6 +366,66 @@ public class Solution {
 }
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    private var board: [[Character]]
+    private var word: String
+    private var m: Int
+    private var n: Int
+
+    init() {
+        self.board = []
+        self.word = ""
+        self.m = 0
+        self.n = 0
+    }
+
+    func exist(_ board: [[Character]], _ word: String) -> Bool {
+        self.board = board
+        self.word = word
+        m = board.count
+        n = board[0].count
+
+        for i in 0..<m {
+            for j in 0..<n {
+                if dfs(i, j, 0) {
+                    return true
+                }
+            }
+        }
+        return false
+    }
+
+    private func dfs(_ i: Int, _ j: Int, _ k: Int) -> Bool {
+        if k == word.count {
+            return true
+        }
+        if i < 0 || i >= m || j < 0 || j >= n || board[i][j] != word[word.index(word.startIndex, offsetBy: k)] {
+            return false
+        }
+
+        let temp = board[i][j]
+        board[i][j] = " "
+        let dirs = [-1, 0, 1, 0, -1]
+        var ans = false
+
+        for l in 0..<4 {
+            let ni = i + dirs[l]
+            let nj = j + dirs[l + 1]
+            if dfs(ni, nj, k + 1) {
+                ans = true
+                break
+            }
+        }
+
+        board[i][j] = temp
+        return ans
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof/面试题12. 矩阵中的路径/Solution.swift

@@ -0,0 +1,55 @@
+class Solution {
+    private var board: [[Character]]
+    private var word: String
+    private var m: Int
+    private var n: Int
+
+    init() {
+        self.board = []
+        self.word = ""
+        self.m = 0
+        self.n = 0
+    }
+
+    func exist(_ board: [[Character]], _ word: String) -> Bool {
+        self.board = board
+        self.word = word
+        m = board.count
+        n = board[0].count
+
+        for i in 0..<m {
+            for j in 0..<n {
+                if dfs(i, j, 0) {
+                    return true
+                }
+            }
+        }
+        return false
+    }
+
+    private func dfs(_ i: Int, _ j: Int, _ k: Int) -> Bool {
+        if k == word.count {
+            return true
+        }
+        if i < 0 || i >= m || j < 0 || j >= n || board[i][j] != word[word.index(word.startIndex, offsetBy: k)] {
+            return false
+        }
+
+        let temp = board[i][j]
+        board[i][j] = " "
+        let dirs = [-1, 0, 1, 0, -1]
+        var ans = false
+
+        for l in 0..<4 {
+            let ni = i + dirs[l]
+            let nj = j + dirs[l + 1]
+            if dfs(ni, nj, k + 1) {
+                ans = true
+                break
+            }
+        }
+
+        board[i][j] = temp
+        return ans
+    }
+}