题解 | 二叉搜索树的最近公共祖先

import java.util.*;

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 *   public TreeNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param root TreeNode类
     * @param p int整型
     * @param q int整型
     * @return int整型
     */
    public int lowestCommonAncestor (TreeNode root, int p, int q) {
        if (root == null) {
            return -1;
        }
        return lowestCommonAncestor2(root, Math.min(p, q), Math.max(p, q));
    }

    static public int lowestCommonAncestor2(TreeNode root, int p, int q) {
        if (root == null) {
            return -1;
        }
        //如果值在两者之间，则之间返回
        if (p <= root.val && root.val <= q) {
            return root.val;
        }
        //最大值都比当前值小
        if (q < root.val) {
            //则在左边
            return lowestCommonAncestor2(root.left, p, q);
        }
        //则在右边
        return lowestCommonAncestor2(root.right, p, q);
    }
}