chore: Add new solution to LeetCode 203

Without using pre Node

Author: tan-i-ham

problems/0203.移除链表元素.md

@@ -234,6 +234,27 @@ public ListNode removeElements(ListNode head, int val) {
     }
     return head;
 }
+/**
+ * 不添加虚拟节点and pre Node方式
+ * 时间复杂度 O(n)
+ * 空间复杂度 O(1)
+ * @param head
+ * @param val
+ * @return
+ */
+public ListNode removeElements(ListNode head, int val) {
+    while(head!=null && head.val==val){
+        head = head.next;
+    }
+    ListNode curr = head;
+    while(curr!=null){
+        while(curr.next!=null && curr.next.val == val){
+            curr.next = curr.next.next;
+        }
+        curr = curr.next;
+    }
+    return head;
+}
 ```
 
 Python：