树--python

# coding=utf-8class node(object):    def __init__(self,data=None,left=None,right=None):        self.data=data        self.left=left        self.right=right        #深度def depth(tree):        if tree==None:            return 0        left,right=depth(tree.left),depth(tree.right)        return max(left,right)+1        #前序遍历，先遍历根节点def pre_order(tree):    if tree==None:        return    print(tree.data)    pre_order(tree.left)    pre_order(tree.right)    #中序遍历def mid_order(tree):    if tree==None:        return    mid_order(tree.left)    print(tree.data)    mid_order(tree.right)    #后序遍历def post_order(tree):    if tree==None:        return    post_order(tree.left)    post_order(tree.right)    print(tree.data)#层次遍历def level_order(tree):    if tree==None:        return    q=[]    q.append(tree)    while q:        current=q.pop(0)        print(current.data)        if current.left!=None:            q.append(current.left)        if current.right!=None:            q.append(current.right)#判断是否平衡二叉树def isbalance(tree):    if tree==None:        return True    left,right=depth(tree.left),depth(tree.right)    diff=left-right    if diff<-1 or diff>1:        return False    return isbalance(tree.left)and isbalance(tree.right)if __name__ == '__main__':    tree=node('d',node('b',node('a'),node('c')),node('e',right=node('g',node('f'))))    print('前序遍历：')    pre_order(tree)    print('中序遍历：')    mid_order(tree)    print('后序遍历：')    post_order(tree)    print('层次遍历：')    level_order(tree)    print('深度：%d'%depth(tree))    print('是否为平衡二叉树：%s'%isbalance(tree))