Miért adja ezt a kimenetet a program? C++.

//main.cpp

#include <iostream>

#include <sstream>

#include <array>

#include <string>

typedef unsigned short ushort;

typedef unsigned int uint;

int main()

{

const unsigned short lines(3);

const unsigned short columns(8);

std::array<std::array<std::string, columns>, lines> twodarray;

for(unsigned short i = 0; i < lines; ++i)

{

std::array<std::string, columns> _array;

for(unsigned short j = 0; j < columns; ++j)

{

std::string str;

std::stringstream s;

s << j+1;

s >> str;

_array.at(j) = str;

}

twodarray.at(i) = _array;

}

for(unsigned short i(0); i < lines; ++i)

for(unsigned short j(0); j < columns; ++j)

std::cout << '[' << i << "][" << j << "]: " << twodarray.at(i).at(j) << '\n';

return 0;

}

Kimenetben csak [0][4] től látható a kiíratás miért?

Miért csak [0][4] írja ki az értékeket?