leetcode/173.binary-search-tree-iterator.cpp at main · ming197/leetcode · GitHub

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/*
 * @lc app=leetcode id=173 lang=cpp
 *
 * [173] Binary Search Tree Iterator
 */

// @lc code=start
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) {}
};
#include "bits/stdc++.h"
using namespace std;
class BSTIterator {
public:
    stack<TreeNode*> s;
    BSTIterator(TreeNode* root) {
        partialInorder(root);
    }

    void partialInorder(TreeNode* root){
        while(root != nullptr){
            s.push(root);
            root = root->left;
        }
    }

    int next() {
        TreeNode* top = s.top();
        s.pop();
        partialInorder(top->right);
        return top->val;
    }

    bool hasNext() {
        return !s.empty();
    }
};

/**
 * 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