持续更新中…

• greed.h

# ifndef GREED_H_
# define GREED_H_

#include <iostream>
#include <vector>
#include <string>
#include <queue>


using std::vector;
using std::string;
using std::queue;
using std::cout;
using std::endl;

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) {}
};

// Create Binary Tree with Vector
TreeNode* constructBinaryTree(const vector<int>& vec);

// Pring Binary Tree
void printBinaryTree(TreeNode* root);

void print2DVector(vector<vector<int>>& vec);
void printVector(vector<int>& vec);

# endif

• greed.cpp

#include "greed.h"

// 根据数组构造二叉树
TreeNode* constructBinaryTree(const vector<int>& vec){
    vector<TreeNode*> vecTree(vec.size(), nullptr);     // 根据数组大小构造二叉树指针数组
    TreeNode* root = nullptr;                           // 将根节点指针定义为 nullptr

    // 创建树节点
    for (int i = 0; i < vec.size(); i++){               // 遍历数组
        TreeNode* node = nullptr;                       // 初始化节点为 nullptr
        if (vec[i] != -1) node = new TreeNode(vec[i]);  // 如果当前元素不是-1， 创建一个新节点，其值为 vec[i]
        vecTree[i] = node;                              // 将新节点放入 vecTree 数组中
        if (i == 0) root = node;                        // 如果是第一个元素，则将其设为根节点
    }

    // 连接节点形成树
    for (int i = 0; i * 2 + 1 < vec.size(); i++)
    {
        if (vecTree[i] != nullptr){
            if (i * 2 + 1 < vec.size()) vecTree[i]->left = vecTree[i * 2 + 1];   // 设置左孩子
            if (i * 2 + 2 < vec.size()) vecTree[i]->right = vecTree[i * 2 + 2];   // 设置左孩子
        }
    }

    return root;    // 返回构造二叉树的根节点
}

// 层序打印二叉树
void printBinaryTree(TreeNode* root)
{
    queue<TreeNode*> que;
    if (root != nullptr) que.push(root);                // 如果二叉树根节点不为空，将其放入 que 队列
    vector<vector<int>> result;                         // 存放二叉树结果的二维数组
    while (!que.empty()){
        int size = que.size();                          // 统计每层队列大小
        vector<int> vec;                                // 存放每层

        for (int i = 0; i < size; i++){
            TreeNode* node = que.front();
            que.pop();
            if (node != nullptr){
                vec.push_back(node->val);
                que.push(node->left);
                que.push(node->right);
            }
            else
                vec.push_back(-1);
        }
        result.push_back(vec);
    }

    for (int i = 0; i < result.size(); i++){
        for (int j = 0; j < result[i].size(); j++){
            std::cout << result[i][j] << " ";
        }
        std::cout << std::endl;
    }

}

void print2DVector(vector<vector<int>>& vec){
    if (vec.size() == 0){
        cout << "[]\n";
        return;
    }

    cout << "[";
    for (int i = 0; i < vec.size(); i++){
        cout << "[";
        for (int j = 0; j < vec[i].size(); j++){
            if (j == vec[i].size() - 1)
                cout << vec[i][j];
            else
                cout << vec[i][j] << ", ";
        }
        if (i == vec.size() - 1)
            cout << "]]\n";
        else
            cout << "], ";
    }
}

void printVector(vector<int>& vec){
    if (vec.size() == 0){
        cout << "[]\n";
        return;
    }

    cout << "[";
    for (int i = 0; i < vec.size(); i++){
        if (i == vec.size() - 1)
            cout << vec[i];
        else
            cout << vec[i] << ", ";
    }
    cout << "]\n";
}