Created
August 22, 2020 18:47
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#include <iostream> | |
using std::cout, std::endl; | |
#include <string> | |
using std::string, std::to_string; | |
struct eat { constexpr eat(auto...){} }; | |
constexpr auto Tree(auto left, long val, auto right) { | |
return [=](auto f) { return f(left, val, right); }; | |
} | |
constexpr auto Leaf(long val) { return Tree(eat{}, val, eat{}); } | |
auto TreeVal = [](eat, long val, eat) { return val; }; | |
auto TreeLeft = [](auto left, long, eat) { return left; }; | |
auto TreeRight = [](eat, long, auto right) { return right; }; | |
string traversal(auto tree) { | |
string out; | |
if constexpr (! std::is_same_v<decltype(tree(TreeLeft)),eat>) | |
(out += traversal(tree(TreeLeft))) += " "; | |
out += to_string(tree(TreeVal)); | |
if constexpr (! std::is_same_v<decltype(tree(TreeRight)),eat>) | |
(out += " ") += traversal(tree(TreeRight)); | |
return out; | |
} | |
int main() | |
{ | |
auto l1 = Leaf(5); | |
auto l2 = Leaf(6); | |
auto t1 = Tree(l1, 3, l2); | |
auto l3 = Leaf(7); | |
auto l4 = Leaf(9); | |
auto t2 = Tree(l3, 4, l4); | |
auto t3 = Tree(t1, 8, t2); | |
cout << traversal(t3) << endl; // prints 5 3 6 8 7 4 9 !!! | |
return 0; | |
} |
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