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jianghui-galaxy · Apr 6, 2018 · 1085339 · 1085339
1 parent 4012e90
commit 1085339
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/notes/算法.md b/notes/算法.md
@@ -301,10 +301,12 @@ public class Queue<Item> {
     }
 
     // 出队列
-    public Item dequeue(){
+    public Item dequeue() {
+        if (isEmpty()) return null;
         Node node = first;
         first = first.next;
         N--;
+        if (isEmpty()) last = null;
         return node.item;
     }
 }