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46 lines
1.3 KiB
46 lines
1.3 KiB
#include <string>
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#include <utility> // for std::pair
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#include <iostream>
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#include <cstdint>
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#include <unordered_set>
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#include <unordered_map>
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//#include <set>
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#include <vector>
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#include <algorithm>
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#include "solutions.hpp"
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using namespace std;
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pair<string, string> solve1(istream &input) {
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unordered_set<int64_t> seen;
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unordered_map<int64_t, pair<int64_t, int64_t>> targets;
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string part1;
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string part2;
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bool part1_solved = false;
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bool part2_solved = false;
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for(string line; getline(input, line); ) {
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int64_t number = stoi(line);
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if (!part1_solved && seen.contains(2020 - number)) {
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part1 = to_string((2020 - number) * number);
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part1_solved = true;
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}
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if (!part2_solved) {
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auto search = targets.find(number);
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if (search != targets.end()) {
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part2 = to_string(number * search->second.first * search->second.second);
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part2_solved = true;
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}
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for (int64_t partner : seen) {
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if (number + partner <= 2020) {
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targets[2020 - number - partner] = pair(number, partner);
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}
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}
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}
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if (part1_solved && part2_solved) {
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return pair(part1, part2);
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}
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seen.insert(number);
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}
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return pair(part1, part2);
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}
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