I am trying to figure out a way to generate a sequence of arrays of integers at compile time (using constexpr functions). The sequence is this one:
// first all order 0 numbers
{0, 0, 0},
// then all order 1 numbers (total sum of figures = 1)
{1, 0, 0},
{0, 1, 0},
{0, 0, 1},
// then all order 2 numbers (total sum of figures = 2) in no specific order
{1, 1, 0},
{0, 1, 1},
{1, 0, 1},
{2, 0, 0},
{0, 2, 0},
{0, 0, 2}
// then all order 3 numbers etc... each block in no specific order
Currently I can only write the algorithm to get these arrays in another order
constexpr int M = 5; // maximum figure available, each figure will be from 0 to 5
constexpr int N = (M + 3) * (M + 2) / 2; // total number of arrays to be generated
constexpr std::array<std::array<int, 3>, N> algorithm() {
std::array<std::array<int, 3>, N> ans;
int pos = 0;
for (int i = 0; i <= M; ++i) {
for (int j = 0; j <= M - i; ++j) {
for (int k = 0; k <= M - i - j; ++k) {
ans[pos] = std::array<int, 3>{k, j, i};
++pos;
}
}
}
return ans;
}
This of course gives the arrays in a bad order:
{0, 0, 0},
{1, 0, 0},
{2, 0, 0},
{3, 0, 0},
...
I know this may be impossible to do at compile time, but maybe someone knows any tip for this kind of problems? Thanks for any help.
