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adding day 6 part 2
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@K20shores
K20shores committed Dec 7, 2024
1 parent 97a64fc commit 38a0cd2
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Showing 2 changed files with 89 additions and 62 deletions.
147 changes: 87 additions & 60 deletions 2024/src/day6.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -7,61 +7,73 @@
#include <tuple>
#include <unordered_set>

struct Pos {
struct Pos
{
int y = 0;
int x = 0;

Pos& operator+(const Pos other) {
Pos &operator+(const Pos other)
{
this->x += other.x;
this->y += other.y;
return *this;
}

Pos& operator+=(const Pos& other) {

Pos &operator+=(const Pos &other)
{
this->x += other.x;
this->y += other.y;
return *this;
}

bool operator==(const Pos& other) const {
return this->x == other.x && this->y == other.y;
bool operator==(const Pos &other) const
{
return this->x == other.x && this->y == other.y;
}
};

struct PosHash {
size_t operator()(const Pos& pos) const {
return std::hash<int>()(pos.y) ^ (std::hash<int>()(pos.x) << 1);
}
struct PosHash
{
size_t operator()(const Pos &pos) const
{
return std::hash<int>()(pos.y) ^ (std::hash<int>()(pos.x) << 1);
}
};

struct PosPairHash {
size_t operator()(const std::pair<Pos, Pos>& key) const {
const auto& [pos, dir] = key;
return std::hash<int>()(pos.y) ^ (std::hash<int>()(pos.x) << 1) ^
(std::hash<int>()(dir.y) << 2) ^ (std::hash<int>()(dir.x) << 3);
}
struct PosPairHash
{
size_t operator()(const std::pair<Pos, Pos> &key) const
{
const auto &[pos, dir] = key;
return std::hash<int>()(pos.y) ^ (std::hash<int>()(pos.x) << 1) ^
(std::hash<int>()(dir.y) << 2) ^ (std::hash<int>()(dir.x) << 3);
}
};

struct Data {
struct Data
{
std::vector<std::string> map;
Pos p;
Pos dir;
std::unordered_set<Pos, PosHash> path;
std::unordered_set<std::pair<Pos, Pos>, PosPairHash> position_direction_set;
};

Pos up = {-1, 0};
Pos down = {1, 0};
Pos left = {0, -1};
Pos right = {0, 1};

Pos next_dir(Pos original) {
Pos next_dir(Pos original)
{
return Pos{.y = original.x, .x = -original.y};
}

char get_next_grid_char(const std::vector<std::string>& map, const Pos& p, const Pos& dir, const Pos& obstacle = {-1, -1}) {
if (p.y + dir.y < map.size() && p.x + dir.x < map[0].size()) {
if (p.y + dir.y == obstacle.y && p.x + dir.x == obstacle.x) {
char get_next_grid_char(const std::vector<std::string> &map, const Pos &p, const Pos &dir, const Pos &obstacle = {-1, -1})
{
if (p.y + dir.y < map.size() && p.x + dir.x < map[0].size())
{
if (p.y + dir.y == obstacle.y && p.x + dir.x == obstacle.x)
{
return '#';
}
return map[p.y + dir.y][p.x + dir.x];
Expand All @@ -75,14 +87,17 @@ int part1(Data &data)
Pos dir = data.dir;
std::unordered_set<Pos, PosHash> visited;

while (true) {
char next = get_next_grid_char(data.map, p, dir);
data.position_direction_set.insert({p, dir});
while (true)
{
data.path.insert(p);
visited.insert(p);
if (next == '\0') break;
if (next == '#') {
char next = get_next_grid_char(data.map, p, dir);
if (next == '\0')
break;
while (next == '#')
{
dir = next_dir(dir);
next = get_next_grid_char(data.map, p, dir);
}
p += dir;
}
Expand All @@ -92,34 +107,41 @@ int part1(Data &data)

int part2(const Data &data)
{
return 0;
int cycles = 0;
auto path = data.path;

// for (const auto& obstacle : path) {
for (const auto &obstacle : path)
{
std::unordered_set<std::pair<Pos, Pos>, PosPairHash> visited;

Pos p = data.p;
Pos dir = data.dir;
Pos o = {.y = p.y, .x = p.x - 1};

// if (obstacle == p) continue; // ignore the startin location
while (true) {
char next = get_next_grid_char(data.map, p, dir, o);
if (visited.find({p, dir}) == visited.end()) {
if (obstacle == p)
continue; // ignore the starting location
while (true)
{
if (visited.find({p, dir}) == visited.end())
{
// haven't been here before
visited.insert({p, dir});
}
else {
else
{
cycles += 1;
break;
}
if (next == '\0') break;
if (next == '#') {
char next = get_next_grid_char(data.map, p, dir, obstacle);
if (next == '\0')
break;
while (next == '#')
{
dir = next_dir(dir);
next = get_next_grid_char(data.map, p, dir, obstacle);
}
p += dir;
}
// }
}

return cycles;
}
Expand All @@ -143,8 +165,10 @@ Data parse()
auto p3 = line.find('>');
auto p4 = line.find('<');
auto a = {p1, p2, p3, p4};
for(auto& p : a) {
if (p != std::string::npos) {
for (auto &p : a)
{
if (p != std::string::npos)
{
data.p.y = i;
data.p.x = p;
break;
Expand All @@ -154,19 +178,20 @@ Data parse()
}

char c = data.map[data.p.y][data.p.x];
switch(c) {
case '^':
data.dir = up;
break;
case 'v':
data.dir = down;
break;
case '>':
data.dir = right;
break;
case '<':
data.dir = left;
break;
switch (c)
{
case '^':
data.dir = up;
break;
case 'v':
data.dir = down;
break;
case '>':
data.dir = right;
break;
case '<':
data.dir = left;
break;
}

return data;
Expand Down Expand Up @@ -200,27 +225,29 @@ BENCHMARK_DEFINE_F(BenchmarkFixture, Part2Benchmark)
}
}

BENCHMARK_REGISTER_F(BenchmarkFixture, Part1Benchmark);
BENCHMARK_REGISTER_F(BenchmarkFixture, Part2Benchmark);
BENCHMARK_REGISTER_F(BenchmarkFixture, Part1Benchmark)->Unit(benchmark::kSecond);
BENCHMARK_REGISTER_F(BenchmarkFixture, Part2Benchmark)->Unit(benchmark::kSecond);

int main(int argc, char **argv)
{
Data data = parse();

int answer1 = 5312;
int answer2 = 0;
int answer2 = 1748;

auto first = part1(data);
auto second = part2(data);

std::cout << "Part 1: " << first << std::endl;

auto second = part2(data);
std::cout << "Part 2: " << second << std::endl;

first != answer1 ? throw std::runtime_error("Part 1 incorrect") : nullptr;
second != answer2 ? throw std::runtime_error("Part 2 incorrect") : nullptr;

for (int i = 1; i < argc; ++i) {
if (std::string(argv[i]) == "--benchmark") {
for (int i = 1; i < argc; ++i)
{
if (std::string(argv[i]) == "--benchmark")
{
benchmark::Initialize(&argc, argv);
benchmark::RunSpecifiedBenchmarks();
return 0;
Expand Down
4 changes: 2 additions & 2 deletions 2024/src/day_template.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -75,9 +75,9 @@ int main(int argc, char **argv)
int answer2 = 0;

auto first = part1(data);
auto second = part2(data);

std::cout << "Part 1: " << first << std::endl;

auto second = part2(data);
std::cout << "Part 2: " << second << std::endl;

first != answer1 ? throw std::runtime_error("Part 1 incorrect") : nullptr;
Expand Down

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