diff --git a/problems/0111.二叉树的最小深度.md b/problems/0111.二叉树的最小深度.md
index de36c6f2..bda12ff0 100644
--- a/problems/0111.二叉树的最小深度.md
+++ b/problems/0111.二叉树的最小深度.md
@@ -300,44 +300,63 @@ class Solution {
 递归法：
 
 ```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
+        
         if not root.left and not root.right:
             return 1
-
-        min_depth = 10**9
+        
+        left_depth = float('inf')
+        right_depth = float('inf')
+        
         if root.left:
-            min_depth = min(self.minDepth(root.left), min_depth) # 获得左子树的最小高度
+            left_depth = self.minDepth(root.left)
         if root.right:
-            min_depth = min(self.minDepth(root.right), min_depth) # 获得右子树的最小高度
-        return min_depth + 1
+            right_depth = self.minDepth(root.right)
+        
+        return 1 + min(left_depth, right_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
-        que = deque()
-        que.append(root)
-        res = 1
-
-        while que:
-            for _ in range(len(que)):
-                node = que.popleft()
-                # 当左右孩子都为空的时候，说明是最低点的一层了，退出
+        depth = 0
+        queue = collections.deque([root])
+        
+        while queue:
+            depth += 1 
+            for _ in range(len(queue)):
+                node = queue.popleft()
+                
                 if not node.left and not node.right:
-                    return res
-                if node.left is not None:
-                    que.append(node.left)
-                if node.right is not None:
-                    que.append(node.right)
-            res += 1
-        return res
+                    return depth
+            
+                if node.left:
+                    queue.append(node.left)
+                    
+                if node.right:
+                    queue.append(node.right)
+
+        return depth
 ```