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) {
        // write code here
        if (root == null) return -1;
        if (root.val == p || root.val == q) return root.val;
        int leftRes = -1;
        if (root.val > p || root.val > q)
            leftRes = lowestCommonAncestor(root.left, p, q);
        int rightRes = -1;
        if (root.val < p || root.val < q)
            rightRes = lowestCommonAncestor(root.right, p, q);
        if (leftRes == p && rightRes == q) return root.val;
        return leftRes != -1 ? leftRes : rightRes;
    }
}