添加 104.二叉树的最大深度 Swift版本

problems/0104.二叉树的最大深度.md

@@ -653,5 +653,82 @@ int maxDepth(struct TreeNode* root){
 }
 ```
 
+## Swift
+
+>二叉树最大深度
+```swift
+// 递归 - 后序
+func maxDepth1(_ root: TreeNode?) -> Int {
+    return _maxDepth1(root)
+}
+func _maxDepth1(_ root: TreeNode?) -> Int {
+    if root == nil {
+        return 0
+    }
+    let leftDepth = _maxDepth1(root!.left)
+    let rightDepth = _maxDepth1(root!.right)
+    return 1 + max(leftDepth, rightDepth)
+}
+
+// 层序
+func maxDepth(_ root: TreeNode?) -> Int {
+    guard let root = root else {
+        return 0
+    }
+    var queue = [TreeNode]()
+    queue.append(root)
+    var res: Int = 0
+    while !queue.isEmpty {
+        res += 1
+        for _ in 0 ..< queue.count {
+            let node = queue.removeFirst()
+            if let left = node.left {
+                queue.append(left)
+            }
+            if let right = node.right {
+                queue.append(right)
+            }
+        }
+    }
+    return res
+}
+```
+
+>N叉树最大深度
+```swift
+// 递归
+func maxDepth(_ root: Node?) -> Int {
+    guard let root = root else {
+        return 0
+    }
+    var depth = 0
+    for node in root.children {
+        depth = max(depth, maxDepth(node))
+    }
+    return depth + 1
+}
+
+// 迭代-层序遍历
+func maxDepth1(_ root: Node?) -> Int {
+    guard let root = root else {
+        return 0
+    }
+    var depth = 0
+    var queue = [Node]()
+    queue.append(root)
+    while !queue.isEmpty {
+        let size = queue.count
+        depth += 1
+        for _ in 0 ..< size {
+            let node = queue.removeFirst()
+            for child in node.children {
+                queue.append(child)
+            }
+        }
+    }
+    return depth
+}
+```
+
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 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>