[LeetCode]235. Lowest Common Ancestor of a Binary Search Tree

来源：互联网发布：东方挂馅炒饭知乎编辑：程序博客网时间：2024/06/02 04:37

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：很简单，判断两个节点是否都同时大于或者小于根节点，是的话递归到左或右节点，不是的话根节点就是最近公共祖先

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {        if(root.val>p.val&&root.val>q.val){            return lowestCommonAncestor(root.left,p,q);        }else if(root.val<p.val&&root.val<q.val){            return lowestCommonAncestor(root.right,p,q);        }else{            return root;        }    }}

0 0