How do you dynamically allocate a matrix?

chustar_24391 0
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How do you dynamically allocate a 2D matrix in C++? I have tried based on what I already know:

#include <iostream>

int main(){
    int rows;
    int cols;
    int * arr;
    arr = new int[rows][cols];
 }

It works for one parameter, but now for two. What should I do?

dynamic-data matrix arrays c++
11 Answers

Here is the most clear & intuitive way i know to allocate a dynamic 2d array in C++. Templated in this example covers all cases.

template<typename T> T** matrixAllocate(int rows, int cols, T **M)
{
    M = new T*[rows];
    for (int i = 0; i < rows; i++){
        M[i] = new T[cols];
    }
    return M;
}

... 

int main()
{
    ...
    int** M1 = matrixAllocate<int>(rows, cols, M1);
    double** M2 = matrixAllocate(rows, cols, M2);
    ...
}
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