test about BinaryTree

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public boolean getPath(TreeNode root, TreeNode node, Stack<TreeNode> stack) {
        if (root == null || node == null) {
            return false;
        }
        stack.push(root);
        if (root == node) {
            return true;
        }
        boolean key = getPath(root.left, node, stack);
        if (key) {
            return true;
        }
        key = getPath(root.right, node, stack);
        if (key) {
            return true;
        }
        stack.pop();
        return false;
    }

    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        Stack<TreeNode> stack1 = new Stack<>();
        getPath(root, p, stack1);
        Stack<TreeNode> stack2 = new Stack<>();
        getPath(root, q, stack2);
        int diff = stack1.size() - stack2.size();
        while (diff > 0) {
            diff--;
            stack1.pop();
        }
        while (diff < 0) {
            diff++;
            stack2.pop();
        }
        while (stack1.size() > 0) {
            TreeNode cur = stack1.pop();
            if (Objects.equals(cur, stack2.pop())) {
                return cur;
            }
        }
        return null;
    }
}

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