90 lines
1.9 KiB
C++
90 lines
1.9 KiB
C++
#include <algorithm>
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#include <cstdint>
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#include <string>
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#include <iostream>
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#include <tuple>
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#include <array>
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#include <map>
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#include <doctest.h>
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#include <aocpp/Startup.hpp>
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namespace {
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template <std::size_t N>
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using Banks = std::array<std::int64_t, N>;
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auto Parse(std::istream & in) -> Banks<16> {
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Banks<16> result;
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for (auto & x : result) {
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if (!(in >> x)) {
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throw std::runtime_error{"bad input"};
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}
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}
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return result;
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}
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template <std::size_t N>
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auto Redistribute(Banks<N> & banks) {
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auto it = std::max_element(banks.begin(), banks.end());
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auto val = *it;
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*it++ = 0;
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for (; val > 0; val--) {
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if (it == banks.end()) it = banks.begin();
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(*it++)++;
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}
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}
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template <std::size_t N>
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auto CycleSearch(Banks<N> & banks)
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-> std::pair<std::size_t, std::size_t>
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{
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std::map<Banks<N>, std::size_t> seen {{banks, 0}};
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std::size_t n = 0;
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for(;;) {
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Redistribute(banks);
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n++;
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auto [it, success] = seen.try_emplace(banks, n);
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if (!success) {
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return {n, n - it->second};
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}
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}
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}
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} // namespace
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TEST_SUITE("2017-06 examples") {
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TEST_CASE("example") {
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Banks<4> banks {0, 2, 7, 0};
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SUBCASE("single step") {
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Redistribute(banks);
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REQUIRE(banks == Banks<4>{2, 4, 1, 2});
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Redistribute(banks);
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REQUIRE(banks == Banks<4>{3, 1, 2, 3});
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Redistribute(banks);
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REQUIRE(banks == Banks<4>{0, 2, 3, 4});
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Redistribute(banks);
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REQUIRE(banks == Banks<4>{1, 3, 4, 1});
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Redistribute(banks);
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REQUIRE(banks == Banks<4>{2, 4, 1, 2});
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}
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SUBCASE("full example") {
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auto [p1,p2] = CycleSearch(banks);
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CHECK(p1 == 5);
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CHECK(p2 == 4);
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}
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}
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}
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auto Main(std::istream & in, std::ostream & out) -> void
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{
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auto input {Parse(in)};
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auto const answer = CycleSearch(input);
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out << "Part 1: " << answer.first << std::endl;
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out << "Part 2: " << answer.second << std::endl;
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}
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