diff --git a/problems/0530.二叉搜索树的最小绝对差.md b/problems/0530.二叉搜索树的最小绝对差.md
index db2ca2d4..b19a0dd2 100644
--- a/problems/0530.二叉搜索树的最小绝对差.md
+++ b/problems/0530.二叉搜索树的最小绝对差.md
@@ -184,15 +184,15 @@ class Solution {
         int result = Integer.MAX_VALUE;
         while (cur != null || !stack.isEmpty()) {
             if (cur != null) {
-                stack.push(cur);
-                cur = cur.left; // 左节点入栈
+                stack.push(cur); // 将访问的节点放进栈
+                cur = cur.left; // 左
             }else {
-                cur = stack.pop(); // 右节点入栈
-                if (pre != null) {
+                cur = stack.pop(); 
+                if (pre != null) { // 中
                     result = Math.min(result, cur.val - pre.val);
                 }
                 pre = cur;
-                cur = cur.right;
+                cur = cur.right; // 右
             }
         }
         return result;