173.二叉搜索树迭代器.cpp

/*
 * @lc app=leetcode.cn id=173 lang=cpp
 *
 * [173] 二叉搜索树迭代器
 */
#include <bits/stdc++.h>
using namespace std;
struct TreeNode
{
  int val;
  TreeNode *left;
  TreeNode *right;
  TreeNode() : val(0), left(nullptr), right(nullptr) {}
  TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
  TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
};
struct ListNode
{
  int val;
  ListNode *next;
  ListNode() : val(0), next(nullptr) {}
  ListNode(int x) : val(x), next(nullptr) {}
  ListNode(int x, ListNode *next) : val(x), next(next) {}
};
// @lc code=start
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class BSTIterator
{
private:
  vector<int> nums;
  int p = 0;

public:
  void in_order(TreeNode *root)
  {
    if (!root)
    {
      return;
    }

    in_order(root->left);
    nums.push_back(root->val);
    in_order(root->right);
  }

  BSTIterator(TreeNode *root)
  {
    in_order(root);
  }

  int next()
  {
    return nums[p++];
  }

  bool hasNext()
  {
    return p < nums.size();
  }
};

/**
 * Your BSTIterator object will be instantiated and called as such:
 * BSTIterator* obj = new BSTIterator(root);
 * int param_1 = obj->next();
 * bool param_2 = obj->hasNext();
 */
// @lc code=end