python二进制搜索树

Question

出于某种原因,我似乎无法让"查找"方法起作用.我认为这与范围问题有关... root.val似乎并没有全局更新.我收到一条错误消息,说AtributeError:'int'对象没有属性'val'这是我的代码:

class BinaryNode:
    def __init__(self, v):
        self.val = v
        self.leftChild = None
        self.rightChild = None
    def get(self):
        return self.val
    def set(self, v):
        self.val = v
    def getChildren(self):
        children = []
        if self.leftChild != None:
            children.append(self.leftChild)
        if self.rightChild != None:
            children.append(self.rightChild)
        return children

class Tree:
    def __init__(self):
        self.root = None
    def setRoot(self, node):
        self.root = node
    def size(self):
        if self.root == None:
            return 0
    def subtreeSize(node):
        return 1 + sum(subtreeSize(c) for c in node.getChildren())
        return subtreeSize(self.root)

class BinarySearchTree(Tree):
    def insert(self, val):
        self.insertNode(self.root, val)

    def insertNode(self, node, val):
        if node is None:
            self.setRoot(BinaryNode(val))
        elif val <= node.val:
            node.leftChild = insertNode(BinaryNode(val), val)
        elif val > node.val:
            node.rightChild = insertNode(BinaryNode(val), val)
        else:
            node.val = val


    def find(self, val):
        self.findNode(self.root, val)

    def findNode(self, node, val):
        if node is None:
            return False
        elif val == node.val:
            return True
        elif val < node.val:
            self.findNode(val, node.leftChild)
        else:
            self.findNode(val, node.rightChild)


if __name__ == "__main__":
    btree = BinarySearchTree()
    vals = [5]
    for v in vals:
        btree.insert(v)
    tests = [8, 5]
    for t in tests:
        print "find(%i) = %s" % (t, ("True" if btree.find(t) else "False"))

Answer 1

您的findNode()方法有两个问题:

1. 你换了node,并val当你递归调用它的参数.这会导致您的代码尝试查找.val整数值而不是节点.

2. 你忘了返回递归调用结果.

纠正方法:

def find(self, val):
    return self.findNode(self.root, val)

def findNode(self, node, val):
    if node is None:
        return False
    elif val == node.val:
        return True
    elif val < node.val:
        return self.findNode(node.leftChild, val)
    else:
        return self.findNode(node.rightChild, val)

你的下一个问题是你的insertNode方法; 你试图在其中调用一个全局insertNode()函数; 这可能应该是self.insertNode().然而,这种方法有没有返回值,所以你最终设置node.leftChild或node.rightChild到None.

您只想将搜索插入点移交给递归调用,无需使用返回值:

def insert(self, val):
    if self.root is None:
        self.setRoot(BinaryNode(val))
    else:
        self.insertNode(self.root, val)

def insertNode(self, node, val):
    if val <= node.val:
        if node.leftChild:
            self.insertNode(node.leftChild, val)
        else:
            node.leftChild = BinaryNode(val)
    elif val > node.val:
        if node.rightChild:
            self.insertNode(node.rightChild, val)
        else:
            node.rightChild = BinaryNode(val)

通过这些更改,您的简单测试打印:

find(8) = False
find(5) = True