Return a vector or array from a function in C++

Question

I want to create a program that create N matrix due the user input, but i need to return the vector(or array) values and then send them to a function, and again, get by return a vector.

For example:

vector<int> createMatrix(rows, cols){
    for(int x = 0; x < rows; x++){
        for(int y = 0; y < cols; y++){
            cout << "Please, input the values for the row " << x << " and col " << y << endl;
            vector<int> Matrix(...)values;
            cin >> (...);
        }
    }
return Matrix; //here is the point
}

vector<int> mathOperations(operation, matrixA, matrixB){
    (...)
    return vector<int> resultMatrix;
}

int main(int argc, char *argv[]){
    int nMatrix, nRows, nCols;
    cout << "Please, answer how many matrix would you like do be created?" << endl;
    cin >> nMatrix;
    cout << "Thank you, and how many rows your matrix will have?" << endl;
    cin >> nRows;
    cout << "Thank you again, and how many cols?" << endl;
    cin >> nCols;
    cout << "Okey, creating " << nMatrix << " nMatrix for you!" << endl;

    for(int n = 0; n < nMatrix; n++){
        cout << "Please, insert the values for the matrix no" << n+1 << endl;
        vector<int> myMatrix[n] = createMatrix(nRows, nCols);
    }

    /* the rest of my code with functions to print values, create a new vectors by math operations between given arguments
    */

return 0;
}

What is the best way to do this?

Ruslan Osmanov · Accepted Answer · 2016-05-06 08:27:25Z

3

If you're looking for a way to construct 2-dimentional structure using vector, use something like this:

#include <vector>
#include <iostream>

using std::vector;
using std::cout;
using std::cin;

typedef vector<vector<int> > matrix_t;

matrix_t createMatrix(int rows, int cols){
  matrix_t Matrix(rows, vector<int>(cols));

  for(int x = 0; x < rows; x++){
    for(int y = 0; y < cols; y++){
      cout << "Please, input the values for the row "
        << x << " and col " << y << std::endl;
      cin >> Matrix[x][y];
    }
  }
  return Matrix;
}

int main(int argc, char const* argv[])
{
  matrix_t M(createMatrix(2, 2));

  for (int i = 0; i < 2; i++) {
    for (int j = 0; j < 2; j++) {
      cout << M[i][j] << std::endl;
    }

  }

  return 0;
}

edited May 6, 2016 at 8:27

answered May 6, 2016 at 5:26

Ruslan Osmanov

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3 Comments

Ruslan Osmanov Over a year ago

@juanchopanza, yes, reserve doesn't change vector's size, so I need resize. Fixed the answer

juanchopanza Over a year ago

OK, I will remove the comments now. BTW. you can skip the resize loop by initializing the vector like this: matrix_t Matrix(rows, vector<int>(cols));. See my answer to this old question.

Ruslan Osmanov Over a year ago

@juanchopanza, ah, indeed, we can pass a vector as initial item value.

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