Making a matrix out of an array using std::vector - c++

Question

I want to make a program that converts an array into matrix. I made something that sort of works but I'm not quite satisfied with the result. I am getting output that actually makes sense but I don't know what I should change to get the one I want.
The size of matrix doesn't have to be 4x4 it can be whatever in fact I want to make one that can make me a 4x4 out of an array[15].
#include<iostream>
#include<vector>
#include<ctime>
#include<cstdlib>
typedef unsigned int uint;
void print(const std::vector<int>& array)
{
for(uint i=0; i< array.size(); i++)
std::cout << array[i] << " ";
std::cout << "\n" << std::endl;
}
void random(std::vector<int>& array, int size = 4)
{
srand(time(0));
std::vector<std::vector<int>> mat;
for(uint i=0; i<4; i++)
{
for(uint j=0; j<4; j++)
{
array.push_back(rand()%10);
}
mat.push_back(array);
}
print(array);
for(uint i=0; i<4; i++)
{
for(uint j=0; j<4; j++)
{
std::cout << mat[i][j] << " ";
}
std::cout << std::endl;
}
}
main()
{
std::vector<int> A;
random(A);
}
Example of an output since it's random
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4
The one i would like to get would look like this:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16

Answer 1

After you've added array to mat with mat.push_back(array), you need to clear array, otherways array will always grow.
std::vector<std::vector<int>> mat;
for (uint i = 0; i < 4; i++)
{
for (uint j = 0; j < 4; j++)
{
array.push_back(rand() % 10);
}
mat.push_back(array);
array.clear(); // <<<< add this
}
Change the code that prints mat to this:
for (uint i = 0; i < mat.size(); i++)
{
for (uint j = 0; j < mat[i].size(); j++)
{
std::cout << mat[i][j] << " ";
}
std::cout << std::endl;
}
and you'll see what happens if you don't call array.clear() as shown above.