后继者:找出二叉搜索树中指定节点的“下一个”节点

后继者:

设计一个算法，找出二叉搜索树中指定节点的“下一个”节点（也即中序后继）。

如果指定节点没有对应的“下一个”节点，则返回null。
来源：力扣（LeetCode）
链接：https://leetcode.cn/problems/successor-lcci

public class InorderSuccessor {
    public static TreeNode inorderSuccessor(TreeNode root, TreeNode p) {
        Deque<TreeNode> stack = new ArrayDeque<TreeNode>();
        TreeNode prev = null, curr = root;
        while (!stack.isEmpty() || curr != null) {
            while (curr != null) {
                stack.push(curr);
                curr = curr.left;
            }
            curr = stack.pop();
            if (prev == p) {
                return curr;
            }
            prev = curr;
            curr = curr.right;
        }
        return null;
    }

    public static void main(String[] args) {
        TreeNode root = new TreeNode(2);
        TreeNode tn1 = new TreeNode(1);
        TreeNode tn2 = new TreeNode(3);
        root.setLeft(tn1);
        root.setRight(tn2);
        TreeNode tn = inorderSuccessor(root,tn1);
        System.out.println(tn);
    }
}