235. 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.

思路:因为是一课BST树，如果这个值在p,q之间就是要的结果，如果比p小，在右子树上，如果比q大，在左子树上

代码如下(已通过leetcode)

public class Solution {
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
   if(root.val<Math.min(p.val, q.val)) return lowestCommonAncestor(root.right, p, q);
   if(root.val>Math.max(p.val, q.val)) return lowestCommonAncestor(root.left, p, q);
   return root;
    }
}