60 lines
1.3 KiB
C++
60 lines
1.3 KiB
C++
#include <fstream>
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#include <iostream>
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#include <set>
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#include <string>
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constexpr int TARGET_NUM = 2020;
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/**
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* Read the input and get it as a set of integers
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* @param filename The filename to read from
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* @return std::set<int> A set of the numbers in the input
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*/
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std::set<int> readInput(const std::string &filename) {
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std::set<int> 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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int num = std::stoi(line);
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input.insert(num);
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}
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return input;
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}
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int part1(const std::set<int> &inputs) {
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for (int num : inputs) {
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int desired = TARGET_NUM - num;
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if (inputs.find(desired) != inputs.end()) {
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return desired * num;
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}
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}
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throw std::runtime_error("Does not contain solution");
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}
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int part2(const std::set<int> &inputs) {
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for (int num : inputs) {
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for (int num2 : inputs) {
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int desired = TARGET_NUM - (num + num2);
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if (inputs.find(desired) != inputs.end()) {
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return desired * num2 * num;
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}
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}
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}
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throw std::runtime_error("Does not contain solution");
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}
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int main(int argc, const char *argv[]) {
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if (argc != 2) {
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std::cerr << "./day1 <input_file>" << std::endl;
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return 1;
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}
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std::set<int> inputs = readInput(argv[1]);
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std::cout << part1(inputs) << std::endl;
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std::cout << part2(inputs) << std::endl;
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}
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