diff --git a/docs/notes/Leetcode 题解.md b/docs/notes/Leetcode 题解.md
index f60ed174..78fcf803 100644
--- a/docs/notes/Leetcode 题解.md	
+++ b/docs/notes/Leetcode 题解.md	
@@ -403,10 +403,12 @@ public List<Integer> topKFrequent(int[] nums, int k) {
     }
     List<Integer> topK = new ArrayList<>();
     for (int i = buckets.length - 1; i >= 0 && topK.size() < k; i--) {
-        if (buckets[i].size() <= (k - topK.size())) {
-            topK.addAll(buckets[i]);
-        } else {
-            topK.addAll(buckets[i].subList(0, k - topK.size()));
+        if (buckets[i] != null) {
+            if (buckets[i].size() <= (k - topK.size())) {
+                topK.addAll(buckets[i]);
+            } else {
+                topK.addAll(buckets[i].subList(0, k - topK.size()));
+            }
         }
     }
     return topK;