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）

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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 ydef 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 xdef 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 ydef 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 xif __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)]

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