Question

我正在尝试用球拍打造一棵树。目前我已经构建了一个“静态”树，仅用于测试插入方法。它在树上运行到正确的位置，但无法插入新节点。

这是树：

(define bst
  (make-node 4
             (make-node 2 empty 
                        (make-node 3 empty empty))
             (make-node 5 empty
                        (make-node 11 empty 
                                   (make-node 12 empty
                                   (make-node 13 empty empty))))))

插入方法（我留下了所有调试打印，因此很容易看到发生了什么，树是正确的）：

(define (insert ABB val)
  (cond[(empty? ABB)(make-node val empty empty)]
       [(< val (node-val ABB))
        (cond
          [(empty? (node-left ABB))
             (printf "\nEntered here\n")
             (node-left ABB)(make-node val empty empty) ; this doesn't work
             (printf "\nABB node-left: ~a" (node-left ABB))
             (printf "\nABB node-left: ~a" (node-val ABB))]
             [else 
              (printf "\nABB node-left (else): ~a" (node-left ABB))
              (insert ((node-left ABB) val))]
             )
        ]
       [(> val (node-val ABB))
        (cond
          [(empty? (node-right ABB))
             (node-left ABB)(make-node val empty empty) ; this doesn't work
             (printf "\nABB node-val (empty): ~a" (node-val ABB))
             (printf "\nEntered here 2\n")
             (node-right ABB)(make-node val empty empty)
             (printf "\nABB node-r:")])]
         [else 
           (printf "\nABB node-val (else): ~a" (node-val ABB))
           (printf "\nABB node-right (else): ~a" (node-right ABB))
           (insert (node-right ABB) val)])
        ]
       )
  )

之后我试图插入17：

(insert bst 17)

以列表形式打印树：

(define (tree->list tree)
  (if (empty? tree)
      empty
      (append (tree->list (node-right tree))
              (cons (node-val tree)
                    (tree->list (node-left tree))))))


(printf "\n\nPrinting tree as list: \n")
(tree->list bst)

输出：

Printing tree as list: 
'(13 12 11 5 4 3 2)

'17'没有显示出来。我无法将新节点分配给当前节点的左/右字段（ABB指向它）。这有什么问题？

Racket：将节点插入树中

0 个答案: