109 lines
2.4 KiB
C++
109 lines
2.4 KiB
C++
#include <cstdint>
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#include <iostream>
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#include <sstream>
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#include <string>
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#include <vector>
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#include <tuple>
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#include <doctest.h>
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#include <aocpp/Startup.hpp>
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using namespace aocpp;
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namespace {
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auto Parse(std::istream & in)
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-> std::vector<std::vector<std::uint16_t>>
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{
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std::string line;
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std::vector<std::vector<std::uint16_t>> result;
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while (std::getline(in, line)) {
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line.erase(std::remove_if(line.begin(), line.end(), [](auto c) {
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return c=='<' || c=='-' || c=='>' || c == ',';
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}), line.end());
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std::istringstream lin { line };
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std::uint16_t x;
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lin >> x;
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std::vector<std::uint16_t> links;
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while (lin >> x) {
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links.push_back(x);
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}
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result.emplace_back(std::move(links));
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}
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return result;
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}
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auto Find(std::vector<std::uint16_t> & leaders, std::uint16_t const who) -> std::uint16_t
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{
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std::uint16_t cursor;
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std::uint16_t leader = who;
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do {
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cursor = leader;
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leader = leaders[cursor];
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} while (leader != cursor);
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cursor = who;
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while (cursor != leader) {
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auto tmp = leaders[cursor];
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leaders[cursor] = leader;
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cursor = tmp;
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}
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return leader;
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}
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auto LinkNodes(std::vector<std::vector<std::uint16_t>> const& input)
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-> std::pair<std::size_t, std::size_t>
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{
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// Allocate leaders array and assign each node as its own leader
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std::vector<std::uint16_t> leaders(input.size());
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for (std::size_t i = 0; i < leaders.size(); i++) {
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leaders[i] = i;
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}
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// Link up all the nodes as specified in the input file
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for (std::size_t i = 0; i < input.size(); i++) {
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auto x_ = Find(leaders, i);
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for (auto const y : input[i]) {
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leaders[Find(leaders,y)] = x_;
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}
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}
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std::size_t part1 = 0;
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std::size_t part2 = 0;
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auto target1 = Find(leaders, 0);
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for (std::size_t i = 0; i < leaders.size(); i++) {
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if (Find(leaders, i) == target1) part1++;
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if (leaders[i] == i) part2++;
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}
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return {part1, part2};
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}
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} // namespace
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TEST_SUITE("2017-12 examples") {
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TEST_CASE("example") {
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std::istringstream in {
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"0 <-> 2\n"
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"1 <-> 1\n"
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"2 <-> 0, 3, 4\n"
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"3 <-> 2, 4\n"
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"4 <-> 2, 3, 6\n"
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"5 <-> 6\n"
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"6 <-> 4, 5\n"};
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auto [p1,p2] = LinkNodes(Parse(in));
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CHECK(p1 == 6);
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CHECK(p2 == 2);
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}
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}
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auto main(int argc, char** argv) -> int {
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auto input = Parse(*Startup(argc, argv));
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auto [part1, part2] = LinkNodes(input);
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std::cout << "Part 1: " << part1 << std::endl;
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std::cout << "Part 2: " << part2 << std::endl;
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} |