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peadarpeadar
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day 16, needs a lot of cleanup
1 parent cf04f60 commit e1434d7

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4 files changed

+174
-6
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4 files changed

+174
-6
lines changed

‎16/Makefile

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This file was deleted.

‎16/Makefile

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PARTOBJS = part1.o part2.o
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include ../Makefile.inc

‎16/solve.cc renamed to ‎16/part1.cc

Lines changed: 7 additions & 5 deletions
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@@ -19,6 +19,7 @@ struct Point {
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struct Cell {
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char c; // can kill this when done debugging.
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unsigned wall:1;
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std::bitset<4> visited;
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Int costs[4] = { MAX, MAX, MAX, MAX };
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Cell(char c) : c(c), wall(c == '#') {}
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};
@@ -36,6 +37,7 @@ constexpr Direction rotate(Direction d) noexcept {
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return Direction((d + 1) % 4);
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}
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[[maybe_unused]]
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std::ostream & operator << (std::ostream &os, Direction d) {
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switch (d) {
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case NORTH: return os << "NORTH";
@@ -68,12 +70,12 @@ struct Part {
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auto head = Q.begin();
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auto item = *head;
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Q.erase(head);
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at(item.pos).costs[item.d] = item.cost; // we now have the shortest path to this item.
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std::cout << "cost to row=" << item.pos.row << ", col=" << item.pos.col << " in direction " << item.d << " is " << item.cost <<"\n";
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at(item.pos).visited[item.d] = true; // we now have the shortest path to this item.
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//std::cout << "cost to row=" << item.pos.row << ", col=" << item.pos.col << " in direction " << item.d << " is " << item.cost <<"\n";
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auto try_add = [&](Point p, Direction d, Int c) {
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auto &cell = at(p);
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if (!cell.wall && cell.costs[d] == MAX) {
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if (!cell.wall && !cell.visited[d] && cell.costs[d] > c) {
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Q.insert({.cost=c, .d=d, .pos=p });
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}
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};
@@ -85,7 +87,7 @@ struct Part {
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d = rotate(d);
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try_add(item.pos, d, item.cost + 2000);
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d = rotate(d);
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try_add(item.pos, d, item.cost + 2000);
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try_add(item.pos, d, item.cost + 1000);
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assert(!Q.empty());
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}
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return Q.begin()->cost;
@@ -115,7 +117,7 @@ struct Part {
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struct Part1 : Part {
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Part1(std::istream &is) noexcept : Part(is) { }
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Int solve(std::ostream &os) {
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Int solve(std::ostream &) {
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return dijkstra();
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}
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};

‎16/part2.cc

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#include "aoc.h"
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namespace {
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enum Direction { NORTH, EAST, SOUTH, WEST };
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using Scalar = unsigned;
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using Int = unsigned long;
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constexpr unsigned long MAX = std::numeric_limits<unsigned long>::max();
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struct Point {
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Scalar row{}, col{};
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Point operator+ (const Point &rhs) const noexcept {
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return { uint8_t(row + rhs.row), uint8_t(col + rhs.col) };
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}
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auto operator <=> (const Point &rhs) const = default;
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};
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struct Cell {
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char c; // can kill this when done debugging.
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unsigned wall:1;
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Int costs[4] = { MAX, MAX, MAX, MAX };
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Cell(char c) : c(c), wall(c == '#') {}
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};
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constexpr Point velocity(Direction d) noexcept {
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switch (d) {
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case NORTH: return {Scalar(-1), 0};
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case SOUTH: return {1, 0};
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case EAST: return {0, 1};
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case WEST: return {0, Scalar(-1)};
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default: __builtin_unreachable();
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}
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}
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constexpr Direction rotate(Direction d) noexcept {
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return Direction((d + 1) % 4);
37+
}
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[[maybe_unused]]
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std::ostream & operator << (std::ostream &os, Direction d) {
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switch (d) {
42+
case NORTH: return os << "NORTH";
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case SOUTH: return os << "SOUTH";
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case EAST: return os << "EAST";
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case WEST: return os << "WEST";
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default: __builtin_unreachable();
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}
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}
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struct Key {
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Point pos;
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Direction d;
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auto operator <=> (const Key &rhs) const = default;
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};
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struct Node {
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unsigned long cost { MAX };
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Key key;
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auto operator <=> (const Node &rhs) const = default;
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};
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struct Part2 {
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std::vector<std::vector<Cell>> map;
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std::vector<std::vector<std::array<std::vector<Key>, 4>>> paths;
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Point s, e;
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Cell & at(Point p) {
68+
return map[p.row][p.col];
69+
}
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void visit(Key k, std::set<Point> &best_points) {
72+
best_points.insert(k.pos);
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if (k.pos != s) {
74+
for (auto &k2 : paths[k.pos.row][k.pos.col][k.d])
75+
visit(k2, best_points);
76+
}
77+
}
78+
79+
Int dijkstra() {
80+
std::set<Node> Q;
81+
Q.insert({.cost=0, .key={.pos = s, .d=EAST}});
82+
while (!Q.empty()) {
83+
auto head = Q.begin();
84+
auto item = *head;
85+
Q.erase(head);
86+
87+
auto try_add = [&](Key to, Int c, Key prev) {
88+
auto &cell = at(to.pos);
89+
if (!cell.wall) {
90+
if (cell.costs[to.d] == c) {
91+
paths[to.pos.row][to.pos.col][to.d].push_back(prev);
92+
} else if (cell.costs[to.d] > c) {
93+
paths[to.pos.row][to.pos.col][to.d].clear();
94+
paths[to.pos.row][to.pos.col][to.d].push_back(prev);
95+
Q.insert({.cost=c, .key=to});
96+
cell.costs[to.d] = c;
97+
}
98+
}
99+
};
100+
101+
Direction d = item.key.d;
102+
try_add(Key{item.key.pos + velocity(d), d}, item.cost + 1, item.key);
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d = rotate(d);
104+
try_add({item.key.pos, d}, item.cost + 1000, item.key);
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d = rotate(d);
106+
try_add({item.key.pos, d}, item.cost + 2000, item.key);
107+
d = rotate(d);
108+
try_add({item.key.pos, d}, item.cost + 1000, item.key);
109+
}
110+
auto ecell = at(e);
111+
auto ebest = *std::min_element( ecell.costs, ecell.costs + 4 );
112+
std::set<Point> best_points;
113+
114+
for (auto dir : { NORTH, SOUTH, EAST, WEST })
115+
if (ecell.costs[dir] == ebest)
116+
visit({e, dir}, best_points);
117+
return best_points.size();
118+
}
119+
120+
Part2(std::istream &is) noexcept {
121+
unsigned row = 0;
122+
for (std::string line; getline(is, line); ) {
123+
map.emplace_back();
124+
paths.emplace_back();
125+
unsigned col = 0;
126+
for (auto c : line) {
127+
map.back().emplace_back(c);
128+
paths.back().emplace_back();
129+
switch (c) {
130+
case 'S':
131+
s = { row, col };
132+
break;
133+
case 'E':
134+
e = { row, col };
135+
break;
136+
}
137+
++col;
138+
}
139+
++row;
140+
}
141+
}
142+
Int solve(std::ostream &) {
143+
return dijkstra();
144+
}
145+
};
146+
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148+
aoc::Case part2{"part2", [](std::istream &is, std::ostream &os) { os << Part2(is).solve(os); } };
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}

‎16/small.txt

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###############
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#.......#....E#
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#.#.###.#.###.#
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#.....#.#...#.#
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#.###.#####.#.#
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#.#.#.......#.#
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#.#.#####.###.#
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#...........#.#
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###.#.#####.#.#
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#...#.....#.#.#
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#.#.#.###.#.#.#
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#.....#...#.#.#
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#.###.#.#.#.#.#
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#S..#.....#...#
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###############

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