int b[2][]={1,2};
时间: 2024-01-09 14:05:52 浏览: 28
This code snippet is invalid in C++. The array declaration has two empty brackets, which is not allowed. In C++, the size of the array must be specified in at least one dimension.
If we assume that the intention was to create a 2D array with 2 rows and unknown number of columns, it could be declared as follows:
```
int b[2][];
```
However, this is still invalid since the size of the second dimension is unknown.
To create a dynamic 2D array with 2 rows and unknown number of columns, we can use pointers and dynamic memory allocation:
```
int** b = new int*[2];
for (int i = 0; i < 2; i++) {
b[i] = new int[numColumns];
}
```
where `numColumns` is the desired number of columns. This creates an array with 2 rows and `numColumns` columns. Remember to deallocate the memory using `delete[]` when it's no longer needed:
```
for (int i = 0; i < 2; i++) {
delete[] b[i];
}
delete[] b;
```