二叉树的遍历和添加结点
class Node():
def __init__(self, item):
self.elem = item
self.l_child = None
self.r_child = None
class Tree():
def __init__(self):
self.root = None
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 is None:
self.root = node
return
else:
queue = []
queue.append(self.root)
# 对已有节点进行层次遍历
while queue:
# 弹出队列的第一个元素
cur = queue.pop(0)
if cur.l_child == None:
cur.l_child = node
return
elif cur.r_child == None:
cur.r_child = node
return
else:
# 如果左右子树都不为空，加入队列继续判断
queue.append(cur.l_child)
queue.append(cur.r_child)
def preorder(self, root):
if root == None:
return
print(root.elem, end='')
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, end=" ")
self.inorder(root.rchild)
def postorder(self, root):
"""递归实现后续遍历"""
if root == None:
return
self.postorder(root.lchild)
self.postorder(root.rchild)
print(root.elem, end=" ")
# ×××××××××× 广度优先遍历 ×××××××××
# 从树的root开始，从上到下从从左到右遍历整个树的节点
def breadth_travel(self):
"""利用队列实现树的层次遍历"""
if self.root == None:
return
queue = [self.root]
while queue:
node = queue.pop(0)
print(node.elem, end=" ")
if node.lchild != None:
queue.append(node.lchild)
if node.rchild != None:
queue.append(node.rchild)
