添加 111.二叉树的最小深度 Swift版本

problems/0111.二叉树的最小深度.md

@@ -404,8 +404,51 @@ var minDepth = function(root) {
 };
 ```
 
+## Swift
 
+> 递归
+```Swift
+func minDepth(_ root: TreeNode?) -> Int {
+    guard let root = root else {
+        return 0
+    }
+    if root.left == nil && root.right != nil {
+        return 1 + minDepth(root.right)
+    }
+    if root.left != nil && root.right == nil {
+        return 1 + minDepth(root.left)
+    }
+    return 1 + min(minDepth(root.left), minDepth(root.right))
+}
+```
 
+> 迭代
+```Swift
+func minDepth(_ root: TreeNode?) -> Int {
+    guard let root = root else {
+        return 0
+    }
+    var res = 0
+    var queue = [TreeNode]()
+    queue.append(root)
+    while !queue.isEmpty {
+        res += 1
+        for _ in 0 ..< queue.count {
+            let node = queue.removeFirst()
+            if node.left == nil && node.right == nil {
+                return res
+            }
+            if let left = node.left {
+                queue.append(left)
+            }
+            if let right = node.right {
+                queue.append(right)
+            }
+        }
+    }
+    return res
+}
+```
 
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