牛客-TOP101-BM37

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
        ArrayList<Integer> pp = getPath(root, p);
        ArrayList<Integer> qq = getPath(root, q);
        int res = 0;
        for(int i = 0 ; i < pp.size() && i < qq.size(); i++){
    
            int x = pp.get(i);
            int y = qq.get(i);
            if(x == y)
                res = pp.get(i);
            else
                break;
        }
        return res;
    }
    
    public ArrayList<Integer> getPath(TreeNode root, int target) {
    
        ArrayList<Integer> list = new ArrayList<>();
        TreeNode node = root;
        while(node.val != target && node != null){
    
            list.add(node.val);
            if(node.val > target){
    
                node = node.left;
            }else{
    
                node = node.right;
            }
        }
        list.add(node.val);
        return list;
    }
}