algo/c-cpp/10_recursive/one_two_step.cc

72 lines
2.0 KiB
C++

#include <iostream>
#include <unordered_map>
class SolutionOFOneTwoStep {
private:
static std::unordered_map<size_t, size_t> result_;
public:
enum class POLICY {
RECURSIVE,
NONRECURSIVE
};
private:
size_t recursive(size_t steps) {
auto iter = result_.find(steps);
if (result_.end() != iter) { // found.
return iter->second;
} else {
size_t res = operator()(steps - 1) + operator()(steps - 2);
result_.insert({steps, res});
return res;
}
}
size_t nonrecursive(size_t steps) {
auto iter = result_.find(steps);
if (result_.end() != iter) { // found.
return iter->second;
} else {
size_t start;
for (start = steps; start != 2 and result_.end() == result_.find(start); --start) {}
for (size_t i = start; i != steps; ++i) {
result_.insert({i + 1, result_[i - 1] + result_[i]});
}
return result_[steps];
}
}
public:
size_t operator()(size_t steps, const POLICY policy = POLICY::RECURSIVE) {
if (policy == POLICY::RECURSIVE) {
return recursive(steps);
} else if (policy == POLICY::NONRECURSIVE) {
return nonrecursive(steps);
}
}
static void debug() {
for (auto kv : result_) {
std::cout << kv.first << ' ' << kv.second << std::endl;
}
std::cout << std::endl;
}
};
std::unordered_map<size_t, size_t> SolutionOFOneTwoStep::result_ = {{1, 1}, {2, 2}};
int main() {
SolutionOFOneTwoStep::debug();
std::cout << SolutionOFOneTwoStep()(5, SolutionOFOneTwoStep::POLICY::RECURSIVE) << std::endl;
SolutionOFOneTwoStep::debug();
std::cout << SolutionOFOneTwoStep()(10, SolutionOFOneTwoStep::POLICY::NONRECURSIVE) << std::endl;
SolutionOFOneTwoStep::debug();
std::cout << SolutionOFOneTwoStep()(20, SolutionOFOneTwoStep::POLICY::RECURSIVE) << std::endl;
SolutionOFOneTwoStep::debug();
return 0;
}