创建 std::string 的二维数组的最佳做法

Best practices for creating a two dimensional array of std::strings

本文关键字：最佳二维数组 string 创建 std 更新时间：2023-10-16

我是 c++ 的新手，正在学习如何声明、使用和删除 std：：string 的二维数组。

因为这是一个学习练习，所以我忽略了使用向量的想法(目前(。

我编写了一个程序，用于创建一个小型二维数组，添加数据，然后删除 2D 数组，尝试在此过程中使用最佳实践。

有人可以提出改进建议吗？我最关心的是在使用完 2d 数组后清理它，这样我就可以避免内存泄漏的可能性。

提前谢谢。

#include <iostream>
#include <string>
using namespace std;
void DIM(std::string **marray,unsigned int row,unsigned long cols)
{
if (marray[row] != nullptr) {
delete [] marray[row];
marray[row] = nullptr;
}
marray[row] = new std::string[cols];
}
void DIM_DELETE (std::string **marray,unsigned int row)
{
if (*&marray[row] != nullptr) {
delete[] marray[row];
marray[row] = nullptr;
}
}
void DIM_DELETE_ALL (std::string **marray,unsigned int rows)
{
for (int i=(rows-1); i>-1; i--) {
if (marray[i] != nullptr) {
delete[] marray[i];
marray[i] = nullptr;
}
}//next i
//now take care of marray
if (marray != nullptr) {
delete [] marray;
marray = nullptr;
}
}
std::string **create2darray(unsigned int rows,unsigned int cols)
{
//first create the pointer
std::string **my = nullptr; //create pointer , note: no data portion assigned yet
//now assign a data portion to the pointer (could do above in one step)
my = new std::string*[rows];// elements 0 through rows-1 //assigns data section (an array of std::strings)
//now set newly created rows to nullptr
for (unsigned int i = 0; i<rows; i++) {
my[i] = nullptr;
}
//dim each row for cols columns
for (unsigned int i = 0; i<rows; i++) {
DIM(my,i,cols);//dims the strings (creates data portion) my = new std::string*[x];//
}
return my;//returning a std::string **
}
int main()
{
unsigned int rows = 3;//3 rows (0 through 2)
unsigned int cols = 4;//4 columns (0 through 3)
std::string **myarray = create2darray(rows,cols);//2d array (3 rows, 5 cols)
cout << "2d array created" << endl << endl;
myarray[0][0] = "a0"; //row 0, col 0
myarray[1][0] = "b0"; //row 1, col 0
myarray[2][0] = "c0";
myarray[0][1] = "a1";
myarray[0][2] = "a2";
myarray[0][3] = "a3";
myarray[1][1] = "b1";
myarray[1][2] = "b2";
myarray[1][3] = "b3";
myarray[2][1] = "c1";
myarray[2][2] = "c2";
myarray[2][3] = "c3";
cout << "assigned data to rows 0 to 2 and cols 0 to 3" << endl << endl;
for (unsigned int i=0; i<rows; i++) {
cout << i << ",0: " << myarray[i][0] << " " << i << ",1: " << myarray[i][1] << " " << i << ",2: " << myarray[i][2] <<  " " << i << ",3: " << myarray[i][3] << endl;
}
cout << endl;
cout << "we are done with 2d array, let's delete it" << endl;
//tested dim_delete (seems to work)
/*
DIM_DELETE(myarray,0);//delete [] myarray[0]; myarray[0] = nullptr;
DIM_DELETE(myarray,1);
DIM_DELETE(myarray,2);
//still need to delete myarray
delete [] myarray;
myarray = nullptr;
*/
//delete all rows and delete the std::string that holds the rows
DIM_DELETE_ALL(myarray,rows);
cout << "array deleted, all done" << endl;
//hold cursor so user can see console messages
do {} while(cin.get()!='n');
return 0;
}

如果数组的第二维是常量，我认为您可以使用单个 new 和 delete 运算符。像这样：

#include <stdio.h>
#include <string>
int ROWS = 3;
const int COLS = 4;
typedef std::string arr4[COLS];
int main()
{
arr4 *a;
a = new arr4[ROWS];
for (int i = 0; i < ROWS; i++)
for (int j = 0; j < COLS; j++)
a[i][j] =  std::to_string(j*ROWS + i);
for (int i = 0; i < ROWS; i++)
{
for (int j = 0; j < COLS; j++)
printf("%s ", a[i][j].c_str());
printf("n");
}
printf("n");
delete [] a;
}