删除python中二进制搜索树基本实现中的操作

Question

除了删除操作之外，我几乎完成了Python中的二进制搜索树实现。

到目前为止，在我迄今为止测试的函数的所有用例中： 1.叶节点被正确删除 2.正确删除有两个孩子的节点 3.正确删除根节点

但是我无法删除左子项或右子项的节点。我的Eclipse IDE向我展示了一些语句没有效果（下图中标有黄色的语句），所以我在我的iPython Notebook本地服务器上尝试了该程序，但结果似乎是一样的。 / p>

第43-57行：

我在python程序中错过了什么？请帮帮我。这是我的代码：

prevnode = None

class Node:     
    def __init__(self,data):
        self.data = data
        self.left = None
        self.right = None

def insert(node,info):
    if node.data is None:
        node.data = info
    elif info < node.data:
        if node.left is None:
            node.left = Node(None)
        insert(node.left,info)
    elif info >= node.data:
        if node.right is None:
            node.right = Node(None)
        insert(node.right,info)

def search(node,info):
    if node is None:
        print "Node with the mentioned data is not found"
    if node.data == info:
        print "Found the node containing value held by info"
    elif info < node.data and node.left is not None:
        search(node.left,info)
    elif info > node.data and node.right is not None:
        search(node.right,info) 

def delete(node,info):
    global prevnode
    if info == node.data:
        print "This is the place where info is stored"
        if node.left is None and node.right is None:
            if prevnode.left is not None and prevnode.left.data == node.data:
                prevnode.left = None
                del node
            elif prevnode.right is not None and prevnode.right.data == node.data:
                prevnode.right = None
                del node 
            return                 
        elif node.left is not None and node.right is None:
            if prevnode.left is not None and prevnode.left.data == node.data:
                prevnode.left == node.left
                del node
            elif prevnode.right is not None and prevnode.right.data == node.data:
                prevnode.right == node.left
                del node
            return
        elif node.left is None and node.right is not None:
            if prevnode.left is not None and prevnode.left.data == node.data:
                prevnode.left == node.right
                del node
            elif prevnode.right is not None and prevnode.right.data == node.data:
                prevnode.right == node.right
                del node 
            return           
        elif node.left is not None and node.right is not None:
            node.data = None
            prevnode = node.right
            successor = prevnode.left
            if successor is None:
                node.data = prevnode.data
                node.right = prevnode.right
            elif successor is not None:
                while successor.left is not None:
                    prevnode = successor
                    successor = prevnode.left
                if successor.right is None:
                    node.data = successor.data
                    prevnode.left = None
                    del successor
                elif successor.right is not None:
                    prevnode.left = successor.right
                    node.data = successor.data
                    successor.right = None
                    del successor               
    elif info < node.data:
        print "We will have to go to the left child of the current node"
        prevnode = node
        print "parent of the left child will be prevnode : ",prevnode.data
        delete(node.left,info)
    elif info >= node.data:
        print "We will have to go to the right child of the current node"
        prevnode = node
        print "parent of the right child will be prevnode : ",prevnode.data
        delete(node.right,info)

def display(node,parent):
    if node is not None:
        print "value at this node is ",node.data
        if parent is None:
            print "it is the root node"
        else:
            print "the parent is ",parent.data
    if node.left is not None:
        display(node.left,node)
    if node.right is not None:
        display(node.right,node)
    else:
        return

BST = Node(None)
while True:
    choice = int(raw_input("Please enter your choice 1.Insert, 2.Search, 3.Delete, 4.Display, 5.Exit"))
    if choice == 1:
        num = int(raw_input("Please enter the number you wish to insert"))
        insert(BST,num)
    elif choice == 2:
        num = int(raw_input("Please enter the number you wish to find"))
        search(BST,num)
    elif choice == 3:
        num = int(raw_input("Please enter the number you wish to delete"))
        delete(BST,num)
    elif choice == 4:
        print "Displaying the Tree"
        display(BST,None)
    elif choice == 5:
        break
    else:
        print "Please enter the correct input"

P.S：如果有任何错误的缩进（我很确定没有），它们可以正确缩进

Answer 1

有一个简单的拼写错误。您正在使用==而不是=。

所以不要这样：

    elif node.left is not None and node.right is None:
        if prevnode.left is not None and prevnode.left.data == node.data:
            prevnode.left == node.left
            del node
        elif prevnode.right is not None and prevnode.right.data == node.data:
            prevnode.right == node.left
            del node
        return
    elif node.left is None and node.right is not None:
        if prevnode.left is not None and prevnode.left.data == node.data:
            prevnode.left == node.right
            del node
        elif prevnode.right is not None and prevnode.right.data == node.data:
            prevnode.right == node.right
            del node 
        return

你想这样做：

    elif node.left is not None and node.right is None:
        if prevnode.left is not None and prevnode.left.data == node.data:
            prevnode.left = node.left  # Changed == to =
            del node
        elif prevnode.right is not None and prevnode.right.data == node.data:
            prevnode.right = node.left  # Changed == to =
            del node
        return
    elif node.left is None and node.right is not None:
        if prevnode.left is not None and prevnode.left.data == node.data:
            prevnode.left = node.right  # Changed == to =
            del node
        elif prevnode.right is not None and prevnode.right.data == node.data:
            prevnode.right = node.right  # Changed == to =
            del node 
        return