直接上代碼:

#coding:utf-8

class Node(object):
    """二叉樹節(jié)點"""

    def __init__(self, item):
        super(Node, self).__init__()
        self.item = item
        self.lchild = None
        self.rchild = None


class Tree(object):
    """二叉樹類"""

    def __init__(self):
        super(Tree, self).__init__()
        self.root = None

    def add(self, item):
        """添加節(jié)點"""
        node = Node(item)
        # 判斷當前樹是否為空
        if self.root is None:
            self.root = node
        else:
            queue = []
            queue.append(self.root)
            # 采用隊列存放, 先將根節(jié)點放入隊列中,取出,看是否有左子樹和右子樹,有就放入并且循環(huán)回來看子樹的子樹,沒有則添加
            while queue:
                temp = queue.pop(0)
                # 看做節(jié)點是否為空
                if temp.lchild is None:
                    temp.lchild = node
                    break
                # 看右節(jié)點是否為空
                elif temp.rchild is None:
                    temp.rchild = node
                    break
                # 都不為空,將左節(jié)點和右節(jié)點放入隊列
                else:
                    queue.append(temp.lchild)
                    queue.append(temp.rchild)

    def wide_travel(self):
        """廣度優(yōu)先遍歷(廣序遍歷):從上到下,從左到右.利用隊列"""
        if self.root is None:
            return
        else:
            queue = []
            queue.append(self.root)
            while queue:
                temp = queue.pop(0)
                print(temp.item, end=" ")
                # 如果有左孩子則放入隊列
                if temp.lchild is not None:
                    queue.append(temp.lchild)
                # 如果有右孩子則放入隊列
                if temp.rchild is not None:
                    queue.append(temp.rchild)
            print()

    # 深度遍歷采用了遞歸
    def preorder(self, node):
        """深度遍歷-先序遍歷(根節(jié)點-左子樹-右子樹)"""
        if node is None:
            return
        print(node.item, end=" ")
        self.preorder(node.lchild)
        self.preorder(node.rchild)

    def inorder(self, node):
        """深度遍歷-中序遍歷(左子樹-根節(jié)點-右子樹)"""
        if node is None:
            return
        self.inorder(node.lchild)
        print(node.item, end=" ")
        self.inorder(node.rchild)

    def posorder(self, node):
        """深度遍歷-后序遍歷(左子樹-右子樹-根節(jié)點)"""
        if node is None:
            return
        self.posorder(node.lchild)
        self.posorder(node.rchild)
        print(node.item, end=" ")


if __name__ == '__main__':
    tree = Tree()
    for char in "ABCDEFG":
        tree.add(char)
    print("先序遍歷:")
    tree.preorder(tree.root)
    print("\n中序遍歷:")
    tree.inorder(tree.root)
    print("\n后序遍歷:")
    tree.posorder(tree.root)
    print("\n廣度遍歷:")
    tree.wide_travel()

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