feat: add Swift codes for binary_tree_traversal article

codes/swift/Package.swift

@@ -23,6 +23,8 @@ let package = Package(
         .executable(name: "hash_map", targets: ["hash_map"]),
         .executable(name: "array_hash_map", targets: ["array_hash_map"]),
         .executable(name: "binary_tree", targets: ["binary_tree"]),
+        .executable(name: "binary_tree_bfs", targets: ["binary_tree_bfs"]),
+        .executable(name: "binary_tree_dfs", targets: ["binary_tree_dfs"]),
     ],
     targets: [
         .target(name: "utils", path: "utils"),
@@ -44,5 +46,7 @@ let package = Package(
         .executableTarget(name: "hash_map", dependencies: ["utils"], path: "chapter_hashing", sources: ["hash_map.swift"]),
         .executableTarget(name: "array_hash_map", path: "chapter_hashing", sources: ["array_hash_map.swift"]),
         .executableTarget(name: "binary_tree", dependencies: ["utils"], path: "chapter_tree", sources: ["binary_tree.swift"]),
+        .executableTarget(name: "binary_tree_bfs", dependencies: ["utils"], path: "chapter_tree", sources: ["binary_tree_bfs.swift"]),
+        .executableTarget(name: "binary_tree_dfs", dependencies: ["utils"], path: "chapter_tree", sources: ["binary_tree_dfs.swift"]),
     ]
 )

codes/swift/chapter_tree/binary_tree_bfs.swift

@@ -0,0 +1,42 @@
+/**
+ * File: binary_tree_bfs.swift
+ * Created Time: 2023-01-18
+ * Author: nuomi1 (nuomi1@qq.com)
+ */
+
+import utils
+
+/* 层序遍历 */
+func hierOrder(root: TreeNode) -> [Int] {
+    // 初始化队列，加入根结点
+    var queue: [TreeNode] = [root]
+    // 初始化一个列表，用于保存遍历序列
+    var list: [Int] = []
+    while !queue.isEmpty {
+        let node = queue.removeFirst() // 队列出队
+        list.append(node.val) // 保存结点
+        if let left = node.left {
+            queue.append(left) // 左子结点入队
+        }
+        if let right = node.right {
+            queue.append(right) // 右子结点入队
+        }
+    }
+    return list
+}
+
+@main
+enum BinaryTreeBFS {
+    /* Driver Code */
+    static func main() {
+        /* 初始化二叉树 */
+        // 这里借助了一个从数组直接生成二叉树的函数
+        let node = TreeNode.listToTree(list: [1, 2, 3, 4, 5, 6, 7])!
+        print("\n初始化二叉树\n")
+        PrintUtil.printTree(root: node)
+
+        /* 层序遍历 */
+        let list = hierOrder(root: node)
+        print("\n层序遍历的结点打印序列 = \(list)")
+    }
+}

codes/swift/chapter_tree/binary_tree_dfs.swift

@@ -0,0 +1,70 @@
+/**
+ * File: binary_tree_dfs.swift
+ * Created Time: 2023-01-18
+ * Author: nuomi1 (nuomi1@qq.com)
+ */
+
+import utils
+
+// 初始化列表，用于存储遍历序列
+var list: [Int] = []
+
+/* 前序遍历 */
+func preOrder(root: TreeNode?) {
+    guard let root = root else {
+        return
+    }
+    // 访问优先级：根结点 -> 左子树 -> 右子树
+    list.append(root.val)
+    preOrder(root: root.left)
+    preOrder(root: root.right)
+}
+
+/* 中序遍历 */
+func inOrder(root: TreeNode?) {
+    guard let root = root else {
+        return
+    }
+    // 访问优先级：左子树 -> 根结点 -> 右子树
+    inOrder(root: root.left)
+    list.append(root.val)
+    inOrder(root: root.right)
+}
+
+/* 后序遍历 */
+func postOrder(root: TreeNode?) {
+    guard let root = root else {
+        return
+    }
+    // 访问优先级：左子树 -> 右子树 -> 根结点
+    postOrder(root: root.left)
+    postOrder(root: root.right)
+    list.append(root.val)
+}
+
+@main
+enum BinaryTreeDFS {
+    /* Driver Code */
+    static func main() {
+        /* 初始化二叉树 */
+        // 这里借助了一个从数组直接生成二叉树的函数
+        let root = TreeNode.listToTree(list: [1, 2, 3, 4, 5, 6, 7])!
+        print("\n初始化二叉树\n")
+        PrintUtil.printTree(root: root)
+
+        /* 前序遍历 */
+        list.removeAll()
+        preOrder(root: root)
+        print("\n前序遍历的结点打印序列 = \(list)")
+
+        /* 中序遍历 */
+        list.removeAll()
+        inOrder(root: root)
+        print("\n中序遍历的结点打印序列 = \(list)")
+
+        /* 后序遍历 */
+        list.removeAll()
+        postOrder(root: root)
+        print("\n后序遍历的结点打印序列 = \(list)")
+    }
+}

codes/swift/utils/TreeNode.swift

@@ -14,4 +14,30 @@ public class TreeNode {
         val = x
         height = 0
     }
+
+    public static func listToTree(list: [Int]) -> TreeNode? {
+        let size = list.count
+        if size == 0 {
+            return nil
+        }
+        let root = TreeNode(x: list[0])
+        var queue: [TreeNode] = [root]
+        var i = 0
+        while !queue.isEmpty {
+            let node = queue.removeFirst()
+            i += 1
+            if i >= size {
+                break
+            }
+            node.left = TreeNode(x: list[i])
+            queue.append(node.left!)
+            i += 1
+            if i >= size {
+                break
+            }
+            node.right = TreeNode(x: list[i])
+            queue.append(node.right!)
+        }
+        return root
+    }
 }

docs/chapter_tree/binary_tree_traversal.md

@@ -188,7 +188,24 @@ comments: true
 === "Swift"
 
     ```swift title="binary_tree_bfs.swift"
-
+    /* 层序遍历 */
+    func hierOrder(root: TreeNode) -> [Int] {
+        // 初始化队列，加入根结点
+        var queue: [TreeNode] = [root]
+        // 初始化一个列表，用于保存遍历序列
+        var list: [Int] = []
+        while !queue.isEmpty {
+            let node = queue.removeFirst() // 队列出队
+            list.append(node.val) // 保存结点
+            if let left = node.left {
+                queue.append(left) // 左子结点入队
+            }
+            if let right = node.right {
+                queue.append(right) // 右子结点入队
+            }
+        }
+        return list
+    }
     ```
 
 ## 前序、中序、后序遍历
@@ -452,7 +469,38 @@ comments: true
 === "Swift"
 
     ```swift title="binary_tree_dfs.swift"
+    /* 前序遍历 */
+    func preOrder(root: TreeNode?) {
+        guard let root = root else {
+            return
+        }
+        // 访问优先级：根结点 -> 左子树 -> 右子树
+        list.append(root.val)
+        preOrder(root: root.left)
+        preOrder(root: root.right)
+    }
 
+    /* 中序遍历 */
+    func inOrder(root: TreeNode?) {
+        guard let root = root else {
+            return
+        }
+        // 访问优先级：左子树 -> 根结点 -> 右子树
+        inOrder(root: root.left)
+        list.append(root.val)
+        inOrder(root: root.right)
+    }
+
+    /* 后序遍历 */
+    func postOrder(root: TreeNode?) {
+        guard let root = root else {
+            return
+        }
+        // 访问优先级：左子树 -> 右子树 -> 根结点
+        postOrder(root: root.left)
+        postOrder(root: root.right)
+        list.append(root.val)
+    }
     ```
 
 !!! note