diff --git a/problems/0977.有序数组的平方.md b/problems/0977.有序数组的平方.md
index 250234e1..a10afbfb 100644
--- a/problems/0977.有序数组的平方.md
+++ b/problems/0977.有序数组的平方.md
@@ -278,6 +278,7 @@ class Solution {
      * @return Integer[]
      */
     function sortedSquares($nums) {
+        // 双指针法
         $res = [];
         for ($i = 0; $i < count($nums); $i++) {
             $res[$i] = 0;