找到给定的两个节点的共同祖先的算法

问题描述

如果给我两个节点和树的根.如何找到两个节点的共同祖先?

If two nodes and root of tree are give to me. How to find the common ancestor of two nodes?

推荐答案

这是我发现对 LCA 有用的 Python 实现:-

Hi here's a python implementation that I found useful for LCA :-

class BST(object):
def __init__(self, val=None, right=None, left=None):
    self.val = val
    self.right = right
    self.left = left
    return None

def __nonzero__(self):
    return self.val is not None

def insert(self, item):
    if not self:
        self.val = item
    elif item < self.val:
        if self.left:
            return self.left.insert(item)
        else:
            self.left = BST(val=item)
    elif item > self.val:
        if self.right:
            return self.right.insert(item)
        else:
            self.right = BST(val=item)
    return None

def lca(self, m, n):
    if n < self.val:
        return self.left.lca(m, n)
    elif m > self.val:
        return self.right.lca(m, n)
    else:
        return self.val


if __name__ == "__main__":
b = BST()
for k in [8, 3, 10, 1, 6, 14, 4, 7, 13]:
    b.insert(k)
for pair in [(4, 7), (4, 10), (1, 4), (1, 3), (3, 6)]:
    print b.lca(*pair)

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