python 数据结构之二叉树

Posted 2021-01-11 kailicard

二叉树关键在构建和遍历，python实现相对简单，我们在实现需要用到类，分别设置爱左右子树，根节点，然后从根进行遍历，进行判断，若为空进行树的构建，非空则返回到列表中即可,我在进行遍历时产生了一个错误思想：把根放到树中遍历，这样发现遍历时会产生一个属性缺失的错误，后来浏览数次代码没有发现这个问题，查找了一些资料才意识到，短板：类运用的不熟练。

class Node(object):
    def __init__(self, elem=-1, lchild=None, rchild=None):
        self.elem=elem
        self.lchild=lchild
        self.rchild=rchild

class Tree(object):
    def __init__(self, root=None):
        self.root = root
    def add(self, elem):
        node = Node(elem)
        if self.root == None:
            self.root=node
        else:
            queue=[]
            queue.append(self.root)
            while queue:
               cur = queue.pop(0)
               if cur.lchild == None:
                   cur.lchild=node
                   return
               elif cur.rchild == None:
                   cur.rchild = node
                   return
               else:
                   queue.append(cur.lchild)
                   queue.append(cur.rchild)

    #深度遍历进行三种三种遍历
    def preorder(self, root):
        """递归实现先序遍历"""
        if root == None:
            return
        print(root.elem)
        self.preorder(root.lchild)
        self.preorder(root.rchild)

    def inorder(self, root):
        """递归实现中序遍历"""
        if root == None:
            return
        self.inorder(root.lchild)
        print(root.elem)
        self.inorder(root.rchild)

    def end(self, root):
        """"""
        if root == None:
            return
        self.end(root.lchild)
        self.end(root.rchild)
        print(root.elem)
    #广度遍历
    def rnf(self,root):
        if self.root == None:
            return
        queue=[]
        queue.append(root)
        while queue:
            cur_node=queue.pop(0)
            print(cur_node.elem)
            if cur_node.lchild != None:
                queue.append(cur_node.lchild)
            if cur_node.rchild != None:
                queue.append(cur_node.rchild)

if __name__ == \'__main__\':
    tree=Tree()
    tree.add(0)
    tree.add(1)
    tree.add(2)
    tree.add(3)
    tree.add(4)
    tree.add(5)
    tree.add(6)
    tree.add(7)
    tree.add(8)
    tree.add(9)
    tree.rnf(tree.root)
    tree.preorder(tree.root)
    tree.inorder(tree.root)
    tree.end(tree.root)