Multiplicação de matrizes usando a classe Vector

gistfile1.cpp

#include <iostream>
#include <iomanip>
#include <vector>
using namespace std;

void altera(vector< vector<int> > & v, int i, int j, int x);

int main()
{
    vector< vector<int> > a(2, vector<int>(3));
    vector< vector<int> > b(3, vector<int>(4));
    vector< vector<int> > c(2, vector<int>(4));

    for (int i = 0; i < 2; i++)
    {
        for (int j = 0; j < 3; j++)
        {
            int x;
            cin >> x;
            altera(a, i, j, x);
        }
    }

    for (int i = 0; i < 3; i++)
    {
        for (int j = 0; j < 4; j++)
        {
            int x;
            cin >> x;
            altera(b, i, j, x);
        }
    }

    for (int i = 0; i < 2; i++)
    {
        for (int j = 0; j < 4; j++)
        {
            c[i][j] = 0;

            for (int k = 0; k < 3; k++)
                c[i][j] += a[i][k] * b[k][j];
        }
    }

    for (int i = 0; i < 2; i++)
    {
        for (int j = 0; j < 4; j++)
        {
            if (j == 0)
                cout << setw(4) << c[i][j];
            else
                cout << setw(5) << c[i][j];
        }

        cout << endl;
    }

    return 0;
}

void altera(vector< vector<int> > & v, int i, int j, int x)
{
    v[i][j] = x;
}