70 lines
1.5 KiB
C++
70 lines
1.5 KiB
C++
#include <iostream>
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#include <fstream>
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#include <vector>
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#include <unordered_map>
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int part_1();
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int part_2();
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int main() {
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part_1();
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part_2();
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}
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int part_1() {
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std::unordered_map<int, int> map;
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std::ifstream input("../input.txt");
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std::string line;
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int i = 0;
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while (std::getline(input, line)) {
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std::pair<int, int> pair {std::stoi(line), i};
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map.insert(pair);
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i++;
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}
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for (std::pair<int, int> pair : map) {
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int num = pair.first;
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int compliment = 2020 - num;
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if (map.contains(compliment)) {
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std::cout << (num * compliment) << std::endl;
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return 0;
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}
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}
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return 1;
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}
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int part_2() {
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std::unordered_map<int, int> map;
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std::ifstream input("../input.txt");
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std::string line;
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int i = 0;
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while (std::getline(input, line)) {
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std::pair<int, int> pair {std::stoi(line), i};
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map.insert(pair);
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i++;
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}
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for (std::pair<int, int> first_pair : map) {
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int num = first_pair.first;
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int compliment = 2020 - num;
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// Still two other numbers we gotta find from here
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for (std::pair<int, int> second_pair : map) {
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int second_num = second_pair.first;
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int second_compliment = compliment - second_num;
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if (map.contains(second_compliment)) {
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std::cout << (num * second_num * second_compliment) << std::endl;
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return 0;
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}
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}
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}
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return 1;
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}
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