Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.
According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes v and w as the lowest node in T that has both v and w as descendants (where we allow a node to be a descendant of itself).”
_______6______
/ ___2__ ___8__
/ \ / 0 _4 7 9
/ 3 5
For example, the lowest common ancestor (LCA) of nodes 2 and 8 is 6. Another example is LCA of nodes 2 and 4 is 2, since a node can be a descendant of itself according to the LCA definition.
public class Solution { public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) { if (root == null) { return null; } if ((p.val - root.val) * (q.val - root.val) <= 0) { return root; } return lowestCommonAncestor(p.val - root.val < 0 ? root.left : root.right, p, q); } }
有的时候可以适当合并代码，使得代码更简洁。
Lowest Common Ancestor of a Binary Search Tree Leetcode
原文：http://www.cnblogs.com/aprilyang/p/6353787.html