leetcode:Lowest Common Ancestor of a Binary Search Tree

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.

Have you met this question in a real interview

题目分析：求给定二叉排序树的最近公共祖先
1.当一个节点的值大于等于根节点，另一个节点的值小于等于根节点，则返回根节点
2. 当两个节点的值都小于根节点，在根节点的左边遍历搜索
3. 当两个节点的值都大于根节点，在根节点的右边遍历搜索
代码如下：

public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
	        if((p.val<=root.val&&q.val>=root.val)||(p.val>=root.val&&q.val<=root.val))
	        	return root;
	        else if(p.val<root.val&&q.val<root.val)
	        {
	        	return lowestCommonAncestor(root.left,p,q);
	        }
	        else 
	        {
	        	return lowestCommonAncestor(root.right,p,q);
	        }
	    }