diff --git a/problems/0110.平衡二叉树.md b/problems/0110.平衡二叉树.md
index f3d70a5c..b0ecf44a 100644
--- a/problems/0110.平衡二叉树.md
+++ b/problems/0110.平衡二叉树.md
@@ -670,26 +670,35 @@ bool isBalanced(struct TreeNode* root) {
 ```c
 //计算结点深度
 int getDepth(struct TreeNode* node) {
+    //开辟栈空间
     struct TreeNode** stack = (struct TreeNode**)malloc(sizeof(struct TreeNode*) * 10000);
     int stackTop = 0;
+    //若传入结点存在，将其入栈。若不存在，函数直接返回0
     if(node)
         stack[stackTop++] = node;
     int result = 0;
     int depth = 0;
     
+    //当栈中有元素时，进行迭代遍历
     while(stackTop) {
+        //取出栈顶元素
         struct TreeNode* tempNode = stack[--stackTop];
+        //若栈顶元素非NULL，则将深度+1
         if(tempNode) {
             depth++;
+            //将栈顶元素再次入栈，添加NULL表示此结点已被遍历
             stack[stackTop++] = tempNode;
             stack[stackTop++] = NULL;
+            //若栈顶元素有左右孩子，则将孩子结点入栈
             if(tempNode->left)
                 stack[stackTop++] = tempNode->left;
             if(tempNode->right)
                 stack[stackTop++] = tempNode->right;
+            //更新结果
             result = result > depth ? result : depth;
         }
         else {
+            //若为NULL，则代表当前结点已被遍历，深度-1
             tempNode = stack[--stackTop];
             depth--;
         }