v7

test/structure/link_list/print.dart

@@ -0,0 +1,29 @@
+
+void main(){
+  //  创建一个 2->4->3 的链表对象
+  ListNode listNode = ListNode(2,next: ListNode(4,next: ListNode(3)));
+
+  // 并完成 ListNode#toString 方法，打印 243
+  print(listNode);
+}
+
+class ListNode {
+  int val;
+  ListNode? next;
+
+  ListNode(this.val, {this.next});
+
+  @override
+  String toString(){
+    ListNode? cur = this;
+    String result = "";
+    while( cur!=null){
+      result = result +cur.val.toString();
+      cur = cur.next;
+    }
+    return result;
+  }
+
+
+
+}