#yyds干货盘点# LeetCode程序员面试金典：后继者

class Solution {
    public TreeNode inorderSuccessor(TreeNode root, TreeNode p) {
        Deque stack = new ArrayDeque();
        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;
    }
}