如何在 C++ 中从函数中返回 2D 数组
Jinku Hu
2023年1月30日
2020年11月24日
本文将介绍如何在 C++ 中从函数中返回一个 2D 数组。
在 C++ 中使用指针符号从函数中返回 2D 数组
对于较大的对象，通过指针返回是首选方法，而不是通过值返回。由于二维数组可能会变得相当大，所以最好将指针传递给矩阵的第一个元素，如下面的代码示例所示。需要注意的是，ModifyArr 中的 2D 数组参数是用 arr[][SIZE] 符号定义的，以便在函数作用域中用括号访问其元素。
#include <iostream>
#include <vector>
#include <iomanip>
using std::cout; using std::cin;
using std::endl; using std::string;
using std::vector; using std::setw;
constexpr int SIZE = 4;
int *ModifyArr(int arr[][SIZE], int len)
{
for (int i = 0; i < len; ++i) {
for (int j = 0; j < len; ++j) {
arr[i][j] *= 2;
}
}
return reinterpret_cast<int *>(arr);
}
int main(){
int c_array[SIZE][SIZE] = {{ 1, 2, 3, 4 },
{ 5, 6, 7, 8 },
{ 9, 10, 11, 12 },
{ 13, 14, 15, 16 }};
cout << "input array\n";
for (auto & i : c_array) {
cout << " [ ";
for (int j : i) {
cout << setw(2) << j << ", ";
}
cout << "]" << endl;
}
cout << endl;
int *ptr = ModifyArr(c_array, SIZE);
cout << "modified array\n";
for (int i = 0; i < SIZE; ++i) {
cout << " [ ";
for (int j = 0; j < SIZE; ++j) {
cout << setw(2) << *(ptr + (i * SIZE) + j) << ", ";
}
cout << "]" << endl;
}
cout << endl;
return EXIT_SUCCESS;
}
输出：
input array
[ 1, 2, 3, 4, ]
[ 5, 6, 7, 8, ]
[ 9, 10, 11, 12, ]
[ 13, 14, 15, 16, ]
modified array
[ 2, 4, 6, 8, ]
[ 10, 12, 14, 16, ]
[ 18, 20, 22, 24, ]
[ 26, 28, 30, 32, ]
在 C++ 中使用指向指针的指针从函数中返回 2D 数组
作为一种替代方法，可以使用指针到指针的记法来返回函数中的数组。如果要返回的对象是动态分配的，这种方法比其他方法有优势。通常，一旦指针在调用者范围内返回，就应该修改元素访问表达式。请注意，我们将数组地址转换为 int*，然后再去引用来获取值。
#include <iostream>
#include <vector>
#include <iomanip>
using std::cout; using std::cin;
using std::endl; using std::string;
using std::vector; using std::setw;
constexpr int SIZE = 4;
int **ModifyArr2(int *arr, int len)
{
for (int i = 0; i < len; ++i) {
for (int j = 0; j < len; ++j)
*(arr + (i * len) + j) *= 2;
}
return reinterpret_cast<int **>(arr);
}
int main(){
int c_array[SIZE][SIZE] = {{ 1, 2, 3, 4 },
{ 5, 6, 7, 8 },
{ 9, 10, 11, 12 },
{ 13, 14, 15, 16 }};
cout << "input array\n";
for (auto & i : c_array) {
cout << " [ ";
for (int j : i) {
cout << setw(2) << j << ", ";
}
cout << "]" << endl;
}
cout << endl;
int **ptr2 = ModifyArr2(c_array[0], SIZE);
cout << "modified array\n";
for (int i = 0; i < SIZE; ++i) {
cout << " [ ";
for (int j = 0; j < SIZE; ++j) {
cout << setw(2) << *((int*)ptr2 + (i * SIZE) + j) << ", ";
}
cout << "]" << endl;
}
cout << endl;
return EXIT_SUCCESS;
}
输出：
input array
[ 1, 2, 3, 4, ]
[ 5, 6, 7, 8, ]
[ 9, 10, 11, 12, ]
[ 13, 14, 15, 16, ]
modified array
[ 2, 4, 6, 8, ]
[ 10, 12, 14, 16, ]
[ 18, 20, 22, 24, ]
[ 26, 28, 30, 32, ]
Author: Jinku Hu
Founder of DelftStack.com. Jinku has worked in the robotics and automotive industries for over 8 years. He sharpened his coding skills when he needed to do the automatic testing, data collection from remote servers and report creation from the endurance test. He is from an electrical/electronics engineering background but has expanded his interest to embedded electronics, embedded programming and front-/back-end programming.
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