Leetcode Binary Tree Generator

LC_BT_Helper.cpp

#include <iostream>
#include <vector>
#include <sstream>
#include <queue>
using namespace std;
/**
 * @brief Definition of TreeNode
 */
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) {}
};

/**
 * @brief Convert raw string input into vector.
 * 
 * @param[in] raw Raw string input
 * @return vector<string> 
 */
vector<string> _raw_reader(string raw) {
    vector<string> result;
    istringstream iss(raw);
    string temp;
    const char delim = ',';

    while (getline(iss, temp, delim)) {
        result.emplace_back(move(temp));
    }
    return result;
}
TreeNode* new_node(string s) {
    if (s == "null") {
        return nullptr;
    }
    int num = stoi(s);
    return new TreeNode(num);
}

/**
 * @brief Convert vector into binary tree
 * 
 * @param[in] nodes vector of nodes' value
 * @return struct TreeNode* 
 */
struct TreeNode* _vec2tree(const vector<string> &nodes) {
    if (nodes.size()==0 || nodes[0] == "null") {
        return nullptr;
    }
    deque<TreeNode*> ptr_queue;
    TreeNode* root = new_node(nodes[0]);
    if (nodes.size() == 1) {
        return root;
    }

    TreeNode* cur = root;
    ptr_queue.push_back(cur);
    deque<TreeNode*> ptr_temp;
    
    int i = 1;
    while (ptr_queue.size() && i<nodes.size()) {
        cur = ptr_queue.front();
        cur->left = new_node(nodes[i]);
        ptr_queue.push_back(cur->left);
        i++;
        if (i<nodes.size()) {
            cur->right = new_node(nodes[i]);
            ptr_queue.push_back(cur->right);
        }
        ptr_queue.pop_front();
        i++;
    }
    return root;
}

/**
 * @brief Generate Binary Tree from string.
 * 
 * @param[in] raw Raw string
 * @return TreeNode* root
 */
TreeNode* generate_BT(string raw) {
    if (raw[0] == '[') {
        raw = raw.substr(1, raw.length()-2);
    }
    vector<string> vec = _raw_reader(raw);
    return _vec2tree(vec);
}

/**
 * Demo
*/
int main() {
    string raw = "[10,5,-3,3,2,null,11,3,-2,null,1]";
    TreeNode* root = generate_BT(raw);
}

实现了Leetcode的字符串转二叉树，以满足本地测试需求。
文件末尾给出了个Demo供参考使用。

This .cpp file is for local debugging use.
At the end of file, I give an example, which you can refer from.