103 lines
2.3 KiB
C++
103 lines
2.3 KiB
C++
#include <iostream>
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#include <vector>
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#include <string>
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#include <unordered_map>
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using ull = unsigned long long;
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auto next(ull x) -> std::vector<ull>;
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auto is_prime(ull n) -> bool;
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class Tree
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{
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public:
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ull value;
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std::vector<Tree> children;
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Tree(ull value, std::vector<ull> tree_children) : value(value) {
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for (ull child : tree_children) {
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children.push_back(Tree(child, {}));
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}
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}
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void step() {
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if (children.size() == 0) {
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auto xs = next(value);
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for (auto val : xs) {
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children.push_back(Tree(val, {}));
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}
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return;
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}
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for (auto &child : children) {
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child.step();
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}
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}
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auto longest_path() -> std::vector<ull> {
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if (children.size() == 0) {
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return { value };
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}
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std::vector<ull> max_path;
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int max_length = 0;
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for (auto &child : children) {
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auto temp = child.longest_path();
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if (temp.size() > max_length) {
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max_length = temp.size();
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max_path = temp;
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}
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}
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std::vector<ull> retval = { value };
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retval.insert(retval.end(), max_path.begin(), max_path.end());
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return retval;
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}
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};
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auto next(ull x) -> std::vector<ull> {
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std::vector<ull> new_xs = {};
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ull temp = x * 10;
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for (int i = 0; i < 10; i++) {
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auto temp2 = temp + i;
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if (is_prime(temp2)) {
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new_xs.push_back(temp2);
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}
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}
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return new_xs;
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}
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auto is_prime(ull n) -> bool {
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static std::unordered_map<ull, bool> primes;
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if (primes.count(n) > 0) {
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return primes[n];
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}
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for (int i = 2; i * i <= n; i++) {
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if (n % i == 0) {
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primes[n] = false;
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return false;
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}
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}
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primes[n] = true;
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return true;
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}
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template <typename T>
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auto print_vec(std::vector<T> vec) -> void {
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std::cout << '[';
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for (T &val : vec) {
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std::cout << val << ", ";
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}
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std::cout << "]\n";
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}
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auto main() -> int {
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std::vector<ull> primes;
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for (int i = 2; i < 10000000; i++) {
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if (is_prime(i)) {
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primes.push_back(i);
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}
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}
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Tree tree(0, primes);
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for (int i = 0; i < 200; i++) {
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tree.step();
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print_vec(tree.longest_path());
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}
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}
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