How to pass matrix and int into a class method as parameters? - c++

Question

int main(){
int row1, column1;
cout << "How many rows for first matrix?";
cin >> row1;
cout << "How many columns first matrix?";
cin >> column1;
int org[row1][column1];
cout << "Enter the elements of first matrix: ";
for(int i=0;i<row1;i++){
for(int j=0;j<column1;j++){
cin>>org[i][j];
}
}
for(int i=0;i<row1;i++){
for(int j=0;j<column1;j++){
cout<<org[i][j];
}
cout<<endl;
}
matrixreshape sol;
I have problems passing column1, row1, and matrix org into the matrixReshape function.
cout<<sol.matrixReshape(vector<vector<int> org[row1][column1],row1, column1);
matrixReshape function as follows:
class matrixreshape {
public:
vector<vector<int>> matrixReshape(vector<vector<int>>& nums, int r, int c) {
vector<vector<int>> newMatrix(r, vector<int>(c, 0));

Answer 1

The method matrixReshape needs a vector<vector<int>> as an actual argument. You are trying to pass it a 2D VLA which is not directly convertible.
You need to use vector<vector<int>> for input and pass that to the matrixReshape.
Here's an example:
vector<vector<int>> org( row1 );
for ( int i = 0; i < org.size(); i++ )
{
org[i].resize( column1 );
for ( int j = 0; j < org[i].size(); j++ )
{
cin >> org[i][j];
}
}
// and then pass it
matrixreshape sol;
cout << sol.matrixReshape( org, row1, col1 );
Or, with C++11's range-for loop, it would be like this:
std::size_t rows {0};
std::size_t cols {0};
std::cin >> rows >> cols;
std::vector<std::vector<int>> matrix( rows );
for ( auto& r : matrix )
{
r.resize( cols );
for ( auto& c : r )
{
std::cin >> c;
}
}
matrixreshape sol;
std::cout << sol.matrixReshape( matrix, rows, cols );
Here's a complete working example: https://godbolt.org/z/XPwRMq
In addition, you don't need rows and columns information to pass to matrixReshape() method as the std::vector has size() method. You can use that if you need that.
Another thing is that you have to overload stream insertion operator << for this type to print it with std::cout.
Here's an example (live):
#include <iostream>
#include <vector>
using Matrix = std::vector<std::vector<int>>;
std::ostream& operator<<( std::ostream& os, const Matrix& m )
{
for ( const auto& r : m )
{
for ( const auto& c : r )
{
os << c << ' ';
}
os << '\n';
}
return os;
}
int main()
{
const Matrix m
{
{ 1, 2 },
{ 3, 4 }
};
std::cout << m;
return 0;
}
Output:
1 2
3 4