数据结构_二叉树

二叉树的创建

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

class Tree(object):
    """树类"""
    def __init__(self, root=None):
        self.root = root

    def add(self, elem):
        """为树添加节点"""
        node = Node(elem)
        #如果树是空的，则对根节点赋值
        if self.root == None:
            self.root = node
        else:
            queue = []
            queue.append(self.root)
            #对已有的节点进行层次遍历
            while queue:
                #弹出队列的第一个元素
                cur = queue.pop(0)
                if cur.lchild == None:
                    cur.lchild = node
                    return
                elif cur.rchild == None:
                    cur.rchild = node
                    return
                else:
                    #如果左右子树都不为空，加入队列继续判断
                    queue.append(cur.lchild)
                    queue.append(cur.rchild)

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二叉树的层次遍历

def breadth_travel(self, root):
    """利用队列实现树的层次遍历"""
    if root == None:
        return
    queue = []
    queue.append(root)
    while queue:
        node = queue.pop(0)
        print(node.elem,)
        if node.lchild != None:
            queue.append(node.lchild)
        if node.rchild != None:
            queue.append(node.rchild)

---

二叉树的深度遍历

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 postorder(self, root):
    """递归实现后序遍历"""
    if root == None:
        return
    self.postorder(root.lchild)
    self.postorder(root.rchild)
    print(root.elem)

---

2020-05-07