cpp: double-pointer and double dimensional array

对于一个二维数组如： int aryy[9][9];
求数组元素的总数： sizeof(a) / sizeof(int)
而数组行数则为 ：( sizeof(a) / sizeof(int) )/ ( sizeof(a[0]) / sizeof(int) )
求数组列数： sizeof(a[0])/sizeof(int)
vector<vector<int> > matrix
int row=matrix.size();//行数
int collor=matrix[0].size();//列数
// level-1 pointer declaration
datatype *pointer;

// level-2 pointer declaration
datatype **pointer;

// level-3 pointer declaration
datatype ***pointer;
https://www.geeksforgeeks.org/c-pointer-to-pointer-double-pointer/
https://www.geeksforgeeks.org/how-many-levels-of-pointers-can-we-have-in-c-cpp/

 

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/*****************************************************************//**  * \file   ConsoleTextFileDemoApp.cpp  c++ 14  * \brief    *  *  * \author geovindu  * \date   June 2023  *********************************************************************/ // ConsoleTextFileDemoApp.cpp : 此文件包含 "main" 函数。程序执行将在此处开始并结束。 //https://stackoverflow.com/questions/936687/how-do-i-declare-a-2d-array-in-c-using-new //geovindu Geovin Du #define _UNICODE   #define _CRT_SECURE_NO_WARNINGS   #include <iostream> #include <windows.h> #include <string> #include <string.h> #include <fstream> #include <stdio.h> #include <cstdlib> #include <cstring> #include <iomanip> #include <cstdio> #include <codecvt> #include <assert.h> #include <windows.h> #include <iostream> #include <fstream> #include <io.h> #include <vector> #include <algorithm> #include <ctime> #include <cstdlib> #include <fstream> #include <sstream>     #define UNASSIGNED 0     using namespace std;     /// <summary> /// 打印二维数组 /// </summary> /// <param name="p"></param> /// <param name="rowNum">行</param> /// <param name="coluNum">列</param> void PrintPtr(int** p, int rowNum, int coluNumn) {     for (int i = 0; i < rowNum; i++)     {         for (int j = 0; j < coluNumn; j++)             cout << p[i][j] << "    ";         cout << endl;     } } /// <summary> /// /// </summary> /// <param name="arry"></param> /// <param name="row"></param> void PrintAr2(int arry[][9], int row) {     for (int i = 0; i < row; i++)     {         for (int j = 0; j < 9; j++)             cout << arry[i][j] << " ";         cout << endl;     } }   /// <summary> /// 打印二维数组 /// </summary> /// <param name="p"></param> /// <param name="rowNum"></param> /// <param name="coluNum"></param> void print_p(int** p, int rowNum, int coluNum) {     cout << "\n------------------------" << endl;     for (int i = 0; i < rowNum; i++)     {         for (int j = 0; j < coluNum; j++)         {             cout << p[i][j] << " ";         }         cout << endl;     } }   /// <summary> /// /// </summary> /// <param name="p"></param> /// <param name="RowSize"></param> /// <param name="LineSize"></param> void print_array(int* p, int RowSize, int LineSize) {     int i, j;     for (i = 0; i < RowSize; i++)     {         for (j = 0; j < LineSize; j++)             printf("%d ", *(p + i * LineSize + j));         printf("\n");     } }   /// <summary> /// 初始化二维数组，即给指针p分配内存。这里注意要使用引用 /// 对于一个二维数组如： int a[2][5]; ///求数组元素的总数： sizeof(a) / sizeof(int) ///而数组行数则为 ：(sizeof(a) / sizeof(int)) / (sizeof(a[0]) / sizeof(int)) ///求数组列数： sizeof(a[0]) / sizeof(int) ///vector<vector<int> > matrix ///int row = matrix.size();//行数 ///int col = matrix[0].size();//列数 /// </summary> /// <param name="p"></param> /// <param name="rowNum"></param> /// <param name="coluNum"></param> void init_p(int**& p, int* rowNum, int* coluNum) {     cin >> *rowNum >> *coluNum;     p = new int* [*rowNum];     for (int i = 0; i < *rowNum; i++)     {         p[i] = new int[*coluNum];     } }   /// <summary> /// 一级指针 二维数组 /// </summary> /// <param name="matrix">二维指针</param> /// <param name="rowSize">行</param> /// <param name="colSize">列</param> void print2D(int* matrix, int rowSize, int colSize) {     for (int i = 0; i < rowSize; ++i) {         for (int j = 0; j < colSize; ++j) {             cout << *(matrix + (i * colSize + j)) << " ";         }         cout << endl;     }     cout << endl; } /// <summary> /// 二级指二维数 /// </summary> /// <param name="matrix"></param> /// <param name="rowSize"></param> /// <param name="colSize"></param> void print2D2(int** matrix, int rowSize, int colSize) {     for (int i = 0; i < rowSize; ++i) {         for (int j = 0; j < colSize; ++j) {             //这里必须 重解释成 1级指针，再移位。 //            cout << *( reinterpret_cast<int*>(matrix) + (i * colSize + j)) << " ";             cout << *((int*)matrix + (i * colSize + j)) << " ";         }         cout << endl;     }     cout << endl; }       int main(int argc, char const* argv[]) {     std::cout << "Hello World! 涂聚文！ \n";                 //s1.anssudoku();       //string duname;     //cout << "输入姓名：" << endl;     //cin >> duname;     //cout << "name:" << duname << endl;     int arsudoku[9][9] = {     {0, 0, 0, 0, 0, 9, 0, 5, 0},     {0, 0, 8, 0, 0, 0, 0, 7, 9},     {0, 0, 1, 5, 0, 2, 0, 0, 0},     {3, 0, 0, 0, 1, 0, 5, 0, 7},     {2, 0, 4, 0, 0, 7, 0, 0, 0},     {0, 0, 0, 6, 0, 0, 2, 0, 0},     {0, 0, 0, 0, 7, 0, 3, 4, 0},     {1, 0, 0, 0, 0, 0, 0, 0, 0},     {0, 3, 0, 0, 5, 6, 0, 0, 0}     };             int* pi;     pi = arsudoku[0];     for (int i = 0; i < sizeof(arsudoku) / sizeof(int); i++)     {         cout << "\t" << &arsudoku[i] << endl; //内存地址         //p = arr[i];         cout << *pi++ << endl;     }       cout <<"point"<< * pi << endl;     ///     print2D(reinterpret_cast<int*>(arsudoku), sizeof(arsudoku) / sizeof(arsudoku[0]), sizeof(arsudoku[0]) / sizeof(int));     //调用一级指针二维数据     //print2D2(reinterpret_cast<int **>(arsudoku), 9, 9);     //     print2D2((int**)arsudoku, sizeof(arsudoku) / sizeof(arsudoku[0]),sizeof(arsudoku[0]) / sizeof(int));       int number = 1;       for (auto row = begin(arsudoku); row != end(arsudoku); ++row)     {           for (auto data = begin(*row); data != end(*row); ++data) {               *data = number++;           }       }                     int** p = new int* [9];     for (int i = 0; i < 9; i++)         p[i] = new int[10];     for (int i = 0; i < 9; i++)     {         for (int j = 0; j < 9; j++)             p[i][j] = arsudoku[i][j];     }     cout << "传递数组名" << endl;     PrintAr2(arsudoku, 9);     cout << "传递指针" << endl;     PrintPtr(p, 9, 9);       int i, j;     print_array((int*)arsudoku, 9, 9);     cout << "***********" << endl;     for (i = 0; i <9; i++)     {         for (j = 0; j < 9; j++)             printf("%d ", *(*(arsudoku + i) + j));         printf("\n");     }       wstring allstr;     wstring sname;     wstring stuID;//学号     int num;//编号     double english;//英语成绩     double math;//数学成绩     double cpp;//C++成绩     int location = 0;//位置编号     int flag = 0;//标记是否有对应的编号       wcout << L"请输入新增学生的信息" << endl;     wcout << L"姓名\t" << "学号\t" << "英语\t" << "数学\t" << "C++\t" << endl;     wcin.imbue(locale("chs"));//获取的是中文     wcout.imbue(locale("chs"));     wcin >> sname >> stuID >> english >> math >> cpp;       //allstr = sname + ' ' + stuID;     allstr.append(sname); //C++ wstring::append     allstr.append(L"\t");     allstr.append(stuID);     allstr.append(L"\t");     allstr.append(to_wstring(english));     allstr.append(L"\t");     allstr.append(to_wstring(math));     allstr.append(L"\t");     allstr.append(to_wstring(cpp));       wcout << allstr << endl;     system("pause");     return 0; }     // 运行程序: Ctrl + F5 或调试 >“开始执行(不调试)”菜单 // 调试程序: F5 或调试 >“开始调试”菜单   // 入门使用技巧: //   1. 使用解决方案资源管理器窗口添加/管理文件 //   2. 使用团队资源管理器窗口连接到源代码管理 //   3. 使用输出窗口查看生成输出和其他消息 //   4. 使用错误列表窗口查看错误 //   5. 转到“项目”>“添加新项”以创建新的代码文件，或转到“项目”>“添加现有项”以将现有代码文件添加到项目 //   6. 将来，若要再次打开此项目，请转到“文件”>“打开”>“项目”并选择 .sln 文件 #define UNICODE