// I'm certain this function could be cleaned up, but it will require some
// serious brain storming, so it is a work in progress....
//
// The idea is I want to generate all possible permutations of RPN stacks given
// a set of 4 input integers.
void perms(std::set<int> possible, std::set<int>& all, std::stack<rpn_item> e, std::vector<rpn_item> const& ops) {
// Once the stack is finished evaluate and add to the set
if (e.size() == 7) {
auto test = eval_rpn_stack(e);
if (test > 0 && test != BAD_DIVIDE)
all.insert(test);
return;
}
// The very bottom of the stack MUST be an operator
if (e.size() == 0) {
for (auto i : ops) {
auto tmp = e;
tmp.push(i);
perms(possible, all, tmp, ops);
}
}
// the TOP 2 items in the stack MUST be integers
if (e.size() >= 5) {
for (auto i : possible) {
auto tmp = possible;
auto tmp_e = e;
tmp.erase(i);
tmp_e.push(i);
perms(tmp, all, tmp_e, ops);
}
}
// This is where things get messy...
// I enumerate all possible stack configurations
// There is no visible pattern that I can see and easily program so for now
// this will remain a mess
for (auto n1 = possible.begin(); n1 != possible.end(); ++n1) {
for (auto n2 = std::next(n1); n2 != possible.end(); ++n2) {
auto tmp_p = possible;
tmp_p.erase(*n1); tmp_p.erase(*n2);
for (auto op1 = ops.begin(); op1 != ops.end(); ++op1) {
for (auto op2 = ops.begin(); op2 != ops.end(); ++op2) {
// op op n n
auto n = push_helper(e, {*op1, *op2, *n1, *n2});
perms(tmp_p, all, n, ops);
// op n op n
n = push_helper(e, {*op1, *n1, *op2, *n2});
perms(tmp_p, all, n, ops);
// n op n op
n = push_helper(e, {*n1, *op1, *n2, *op2});
perms(tmp_p, all, n, ops);
// op n n op
n = push_helper(e, {*op1, *n1, *n2, *op2});
perms(tmp_p, all, n, ops);
// n op op n
n = push_helper(e, {*n1, *op1, *op2, *n2});
perms(tmp_p, all, n, ops);
}
}
}
}
}
void push(THandlers&... handlers) {
osmium::item_type type = osmium::item_type::undefined;
while (osmium::memory::Buffer buffer = read()) {
type = push_helper(buffer, type, handlers...);
delete[] buffer.data();
}
push_helper(type, handlers...);
}
void push_helper(osmium::item_type type, THead& handler, TTail&... more) {
handler(type);
push_helper(type, more...);
}
osmium::item_type push_helper(osmium::memory::Buffer& buffer, osmium::item_type type, THead& handler, TTail&... more) {
handler(buffer, type);
return push_helper(buffer, type, more...);
}