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Finish day 12.

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Bert Peters
2019-12-12 18:09:59 +01:00
parent 1a1d5f8b82
commit 09a0a9513b
1 changed files with 41 additions and 7 deletions
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48
2019/src/day12.cpp
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@@ -1,4 +1,5 @@
#include <iostream> #include <iostream>
#include <numeric>
#include <vector> #include <vector>
#include <regex> #include <regex>
#include "days.hpp" #include "days.hpp"
@@ -47,6 +48,14 @@ namespace {
} }
} }
} }
void simulate_step(std::vector<point_t> &moons, std::vector<point_t> &velocities) {
update_velocities(moons, velocities);
for (int j = 0; j < moons.size(); ++j) {
moons[j] += velocities[j];
}
}
} }
void aoc2019::day12_part1(std::istream &input, std::ostream &output) { void aoc2019::day12_part1(std::istream &input, std::ostream &output) {
@@ -54,11 +63,7 @@ void aoc2019::day12_part1(std::istream &input, std::ostream &output) {
std::vector<point_t> velocities(moons.size()); std::vector<point_t> velocities(moons.size());
for (int i = 0; i < 1000; ++i) { for (int i = 0; i < 1000; ++i) {
update_velocities(moons, velocities); simulate_step(moons, velocities);
for (int j = 0; j < moons.size(); ++j) {
moons[j] += velocities[j];
}
} }
int energy = 0; int energy = 0;
@@ -67,9 +72,38 @@ void aoc2019::day12_part1(std::istream &input, std::ostream &output) {
energy += moons[i].l1() * velocities[i].l1(); energy += moons[i].l1() * velocities[i].l1();
} }
output << energy << std::endl; output << energy << std::endl;
} }
void aoc2019::day12_part2(std::istream &input, std::ostream &output) { void aoc2019::day12_part2(std::istream &input, std::ostream &output) {
output << "Not implemented\n"; const auto moons = read_moons(input);
auto moons_mut = moons;
std::vector<point_t> velocities(moons.size());
std::array<uint64_t, 3> recurrence = {0, 0, 0};
std::uint64_t steps = 0;
while (!std::all_of(recurrence.begin(), recurrence.end(), [](auto x) { return x > 0; })) {
simulate_step(moons_mut, velocities);
++steps;
for (int i = 0; i < 3; ++i) {
if (!recurrence[i]) {
bool back_again =
std::all_of(velocities.begin(), velocities.end(), [i](const auto &x) { return !x[i]; })
&& std::equal(moons_mut.begin(), moons_mut.end(), moons.begin(),
[i](const auto &a, const auto &b) {
return a[i] == b[i];
});
if (back_again) {
recurrence[i] = steps;
}
}
}
}
auto result = std::lcm(recurrence[0], std::lcm(recurrence[1], recurrence[2]));
output << result << std::endl;
} }