数据结构与算法分析4 Python创建二叉树采用先、中、后序遍历

 1.Exp4Class创建结点类

# 创建结点类
class Node():
    def __init__(self, data, l=None, r=None):
        self.data = data
        self.l = l
        self.r = r

    # 添加左子树
    def addLeftTree(self, node):
        self.l = node

    # 添加右子树
    def addRightTree(self, node):
        self.r = node

    # 先序遍历：根左右
    def PreTravel(self, DataList):  # DataList存储遍历的数据
        DataList.append(self.data)
        if self.l is not None:  # 子树不为空则递归该方法
            self.l.PreTravel(DataList)
        if self.r is not None:
            self.r.PreTravel(DataList)
        return DataList

    # 中序遍历：左根右
    def MidTravel(self, DataList):
        if self.l is not None:
            self.l.MidTravel(DataList)
        DataList.append(self.data)
        if self.r is not None:
            self.r.MidTravel(DataList)
        return DataList

    # 后序遍历：左右根
    def BackTravel(self, DataList):
        if self.l is not None:
            self.l.BackTravel(DataList)
        if self.r is not None:
            self.r.BackTravel(DataList)
        DataList.append(self.data)
        return DataList

2.Exp4Run：

from Exp4Class import Node

# 创建子树
a = Node(1)
b = Node(2)
c = Node(3)
d = Node(4)
e = Node(5)
f = Node(6)
g = Node(7)
a.addLeftTree(b)
a.addRightTree(f)
b.addRightTree(c)
c.addLeftTree(d)
c.addRightTree(e)
f.addLeftTree(g)

print("先序遍历：{}".format(a.PreTravel([])))
print("中序遍历：{}".format(a.MidTravel([])))
print("后序遍历：{}".format(a.BackTravel([])))