关于二叉查找树中的某个节点的前趋和后继的算法（Python实现）

废话不多说，代码如下：

# -*- coding:utf-8 -*-
def Tree_Predecessor(x):
'''给定一个二叉查找树的节点z，要求找出在中序遍历下它的前趋'''
if left[x] != None:
return Tree_Maximum(left[x])
y = p[x]
while y != None and x == left[y]:
x = y
y = p[y]
return y

def Tree_Maximum(x):
'''找出以x节点为根的树中的最大关键字元素'''
if right[x] != None:
return Tree_Maximum(right[x])
return x

def Tree_Successor(x):
'''给定一个二叉树中的节点z，要求找出在中序遍历顺序下它的后继'''
if right[x] != None:
return Tree_Minimum(right[x])
y = p[x]
while y != None and x == right[y]:
x = y
y = p[y]
return y

def Tree_Minimum(x):
'''找出以x节点为根的树中的最小关键字元素'''
while left[x] != None:
return Tree_Minimum(left[x])
return x

if __name__ == '__main__':
key = [15,6,18,3,7,17,2,4,9,13,20]
left = [1,3,5,6,None,None,None,None,None,8,None]
right = [2,4,10,7,9,None,None,None,None,None,None]
p = [None,0,0,1,1,2,3,3,9,4,2]
print key[Tree_Predecessor(9)]         #输出key[9]=13的前趋和后继
print key[Tree_Successor(9)]