How to set initialize size of std::vector?

[wolfv]

Write your question here.

I am attempting to use vector "fill constructor" to push_back 4 instances of Map.
But got a compile error on the last line below. What is the correct syntax?

Thank you.

#include <vector>
#include <string>
#include <iostream>

struct Map
{
    unsigned int mat=32;
    unsigned int row=32;
    unsigned int col=32;
};

struct Row
{
    std::string scanner;
    std::string pin;
    std::vector<Map> vLayoutToKeyMatrix;
};

struct RowInv
{
    std::vector<Map> vKeyMatrixToLayout;
};

struct Matrix
{
    std::vector<Row> vRows;
    std::vector<RowInv> vRowsInv;
};

std::vector<Matrix> vMatrices;

int main()
{
    vMatrices.push_back(Matrix());

    //instantiate vRows
    vMatrices[0].vRows.push_back(Row());
    vMatrices[0].vRows[0].vLayoutToKeyMatrix.push_back(Map());

    //instantiate vRowsInv
    vMatrices[0].vRowsInv.push_back(RowInv());
    vMatrices[0].vRowsInv[0].vKeyMatrixToLayout.push_back(Map(4));
        //error: expected primary-expression before ‘Map’
}

[JLBorges]

// vMatrices[0].vRowsInv[0].vKeyMatrixToLayout.push_back(Map(4));
vMatrices[0].vRowsInv[0].vKeyMatrixToLayout.resize(4);

[wolfv]

Thanks JLBorges, that compiled nice!