Update 0111.二叉树的最小深度.md

problems/0111.二叉树的最小深度.md

@@ -359,6 +359,39 @@ class Solution:
         return depth
 ```
 
+迭代法：
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+
+class Solution:
+    def minDepth(self, root: TreeNode) -> int:
+        if not root:
+            return 0
+        
+        queue = collections.deque([(root, 1)])
+        
+        while queue:
+            node, depth = queue.popleft()
+            
+            # Check if the node is a leaf node
+            if not node.left and not node.right:
+                return depth
+            
+            # Add left and right child to the queue
+            if node.left:
+                queue.append((node.left, depth+1))
+            if node.right:
+                queue.append((node.right, depth+1))
+        
+        return 0
+
+```
 
 ## Go