C ++双数组初始化错误

Question

我有这个C ++程序：

int box[9][9];
box = {  {solution[0][0],solution[0][1],solution[0][2],solution[1][0],solution[1][1],solution[1][2],solution[2][0],solution[2][1],solution[2][2]},
                          {solution[0][3],solution[0][4],solution[0][5],solution[1][3],solution[1][4],solution[1][5],solution[2][3],solution[2][4],solution[2][5]},
                          {solution[0][6],solution[0][7],solution[0][8],solution[1][6],solution[1][7],solution[1][8],solution[2][6],solution[2][7],solution[2][8]},
                          {solution[3][0],solution[3][1],solution[3][2],solution[4][0],solution[4][1],solution[4][2],solution[5][0],solution[5][1],solution[5][2]},
                          {solution[3][3],solution[3][4],solution[3][5],solution[4][3],solution[4][4],solution[4][5],solution[5][3],solution[5][4],solution[5][5]},
                          {solution[3][6],solution[3][7],solution[3][8],solution[4][6],solution[4][7],solution[4][8],solution[5][6],solution[5][7],solution[5][8]},
                          {solution[6][0],solution[6][1],solution[6][2],solution[7][0],solution[7][1],solution[7][2],solution[8][0],solution[8][1],solution[8][2]},
                          {solution[6][3],solution[6][4],solution[6][5],solution[7][3],solution[7][4],solution[7][5],solution[8][3],solution[8][4],solution[8][5]},
                          {solution[6][6],solution[6][7],solution[6][8],solution[7][6],solution[7][7],solution[7][8],solution[8][6],solution[8][7],solution[8][8]}};

我得到的错误是：

error: assigning to an array from an initializer list

这意味着什么？

Answer 1

声明变量时必须使用初始化程序：

int box[9][9]= {  {solution[0][0],solution[0][1],solution[0][2],solution[1][0],solution[1][1],solution[1][2],solution[2][0],solution[2][1],solution[2][2]},
                          {solution[0][3],solution[0][4],solution[0][5],solution[1][3],solution[1][4],solution[1][5],solution[2][3],solution[2][4],solution[2][5]},
                          {solution[0][6],solution[0][7],solution[0][8],solution[1][6],solution[1][7],solution[1][8],solution[2][6],solution[2][7],solution[2][8]},
                          {solution[3][0],solution[3][1],solution[3][2],solution[4][0],solution[4][1],solution[4][2],solution[5][0],solution[5][1],solution[5][2]},
                          {solution[3][3],solution[3][4],solution[3][5],solution[4][3],solution[4][4],solution[4][5],solution[5][3],solution[5][4],solution[5][5]},
                          {solution[3][6],solution[3][7],solution[3][8],solution[4][6],solution[4][7],solution[4][8],solution[5][6],solution[5][7],solution[5][8]},
                          {solution[6][0],solution[6][1],solution[6][2],solution[7][0],solution[7][1],solution[7][2],solution[8][0],solution[8][1],solution[8][2]},
                          {solution[6][3],solution[6][4],solution[6][5],solution[7][3],solution[7][4],solution[7][5],solution[8][3],solution[8][4],solution[8][5]},
                          {solution[6][6],solution[6][7],solution[6][8],solution[7][6],solution[7][7],solution[7][8],solution[8][6],solution[8][7],solution[8][8]}};

Answer 2

此C ++错误：

error: assigning to an array from an initializer list

引起的原因是您试图为数组分配不允许的初始化程序。 创建数组时会进行初始化，并在创建数组时将值压入其中。 当已经创建数组并将新值放入其中时，就会发生分配。 初始化或分配期间可以执行的操作之间有区别。

这是导致上述错误的最简单的代码：

#include <cstdlib>
#include <iostream>
using namespace std;
int main(int argc, char** argv) {
    int myarray [] = {1,2,4};
    myarray [] = {2,5,9};
    //error, cannot assign with an initializer.
    //You can't initialize an array that's already been initialized.
    return 0;
}

如果要在其中强制输入新值，请尝试std::copy ：

int myarray [] = {1,2,3,4};
int newarray [] = {2,5,9,12};

//copy the first 4 elements from newarray into newarray
std::copy(newarray, newarray + 4, myarray);

for(int x = 0; x < 4; x++){
    cout << myarray[x] << ",";
}

打印： 2,5,9,12,

但是然后您应该问自己，为什么要像这样在金属上接近编程。

考虑使用std :: vector代替 ：

#include <iostream>
#include <vector>
using namespace std;
int main(int argc, char** argv) {
    vector<int> array;
    cout << "size is: " << array.size() << endl;
    array.push_back(42);
    cout << "size is: " << array.size() << endl;
    cout << "data items: " << array.at(0) << endl;
    array.insert(array.begin(), 5);
    array.insert(array.end(), 20);
    cout << "size is: " << array.size() << endl;
    int len = array.size();
    for(int x = 0; x < array.size(); x++){
      cout << "data item: " << array.at(x) << endl;
    }
    return 0;
}

打印此：

size is: 0
size is: 1
data items: 42
size is: 3
data item: 5
data item: 42
data item: 20

使用C ++向量重新初始化列表 ：

#include <iostream>
#include <vector>
using namespace std;
int main() 
{
  int foobar[3] = {1, 2, 3};
  std::vector<int> myvector(foobar, foobar + 3);

  int moobar[3] = {4, 5, 6};
  myvector.assign(moobar, moobar + 3);

  for(int x = 0; x < 3; x++)
      cout << myvector[x];
}