145 lines
3.5 KiB
C++
145 lines
3.5 KiB
C++
#include <folly/String.h>
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#include <algorithm>
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#include <exception>
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#include <fstream>
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#include <iostream>
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#include <numeric>
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#include <regex>
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#include <string>
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#include <vector>
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const std::string POLICY_PATTERN = "([0-9]+)-([0-9]+) (.)";
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const std::string DELIM = ": ";
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/**
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* Policy represents a password policy
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*/
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class Policy {
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public:
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Policy(int min, int max, char letter) : min(min), max(max), letter(letter) {
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}
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/**
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* Parse a policy from an input string
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* @param input The input to parse
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* @return Policy The policy from the input
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*/
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static Policy parse(const std::string &input) {
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std::regex expression(POLICY_PATTERN);
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std::smatch matches;
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if (!std::regex_search(input, matches, expression)) {
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throw new std::invalid_argument("Invalid string");
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}
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return Policy(std::stoi(matches[1]), std::stoi(matches[2]), matches.str(3).at(0));
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}
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int getMin() const {
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return this->min;
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}
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int getMax() const {
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return this->max;
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}
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char getLetter() const {
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return this->letter;
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}
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private:
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int min;
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int max;
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char letter;
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};
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std::vector<std::string> readInput(const std::string &filename) {
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std::vector<std::string> input;
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std::string line;
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std::ifstream file(filename);
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while (std::getline(file, line)) {
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input.push_back(line);
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}
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return input;
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}
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class Entry {
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public:
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Entry(Policy policy, std::string password) : policy(policy), password(password) {
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}
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/**
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* Parse an input entry from an input string
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* @param input The input to parse
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* @return Entry the entry from the input
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*/
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static Entry parse(const std::string &input) {
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int delimIndex = input.find(DELIM);
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std::vector<std::string> components;
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folly::split(DELIM, input, components);
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std::string rawPolicy = components.at(0);
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std::string password = components.at(1);
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Policy policy = Policy::parse(rawPolicy);
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return Entry(policy, password);
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}
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const Policy &getPolicy() const {
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return this->policy;
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}
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const std::string &getPassword() const {
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return this->password;
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}
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private:
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Policy policy;
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std::string password;
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};
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/**
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* Get the number of valid passwords in the input
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* @param input The input split into lines
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* @param matches A function that checks whether or not the password matches the policy
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* @return int The number ofm atching password
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*/
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int getNumValidPasswords(const std::vector<std::string> &input, const std::function<bool(const Entry &)> &valid) {
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return std::accumulate(input.begin(), input.end(), 0, [&](int total, std::string rawEntry) {
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Entry entry = Entry::parse(rawEntry);
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return total + valid(entry);
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});
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}
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int part1(const std::vector<std::string> &input) {
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return getNumValidPasswords(input, [](const Entry &entry) {
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const Policy &policy = entry.getPolicy();
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const std::string &password = entry.getPassword();
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int count = std::count_if(password.begin(), password.end(), [&](char c) { return c == policy.getLetter(); });
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return (count >= policy.getMin() && count <= policy.getMax());
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});
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}
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int part2(const std::vector<std::string> &input) {
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return getNumValidPasswords(input, [](const Entry &entry) {
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const Policy &policy = entry.getPolicy();
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const std::string &password = entry.getPassword();
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char letter = entry.getPolicy().getLetter();
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return ((password.at(policy.getMin() - 1) == letter) ^ (password.at(policy.getMax() - 1) == letter));
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});
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}
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int main(int argc, char *argv[]) {
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if (argc != 2) {
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std::cerr << "./day2 <input_file>" << std::endl;
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return 1;
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}
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auto input = readInput(argv[1]);
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std::cout << part1(input) << std::endl;
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std::cout << part2(input) << std::endl;
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}
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