feat: day 10

2024/src/day10.zig

@@ -0,0 +1,111 @@
+const std = @import("std");
+const utils = @import("utils.zig");
+
+const HikeTrail = enum {
+    Start,
+    One,
+    Two,
+    Three,
+    Four,
+    Five,
+    Six,
+    Seven,
+    Eight,
+    End,
+
+    Empty,
+};
+
+fn parse_map(alloc: std.mem.Allocator, file: []const u8) !std.ArrayList([]HikeTrail) {
+    const width = std.mem.indexOf(u8, file, "\n").?;
+
+    var map = try std.ArrayList([]HikeTrail).initCapacity(alloc, width);
+    errdefer map.deinit();
+
+    var it = std.mem.tokenizeAny(u8, file, "\n");
+    while (it.next()) |raw_line| {
+        var line = try std.ArrayList(HikeTrail).initCapacity(alloc, width);
+        for (raw_line) |tile|
+            line.appendAssumeCapacity(if (tile >= '0' and tile <= '9')
+                @enumFromInt(tile - '0')
+            else if (tile == '.') .Empty else unreachable);
+        map.appendAssumeCapacity(try line.toOwnedSlice());
+    }
+    return map;
+}
+
+const Coordiates = struct {
+    x: i64,
+    y: i64,
+
+    inline fn add(self: Coordiates, other: Coordiates) Coordiates {
+        return .{ .x = self.x + other.x, .y = self.y + other.y };
+    }
+};
+
+fn compute(comptime part_1: bool, map: [][]HikeTrail, pos: Coordiates) usize {
+    var result: usize = 0;
+
+    const expect: HikeTrail =
+        @enumFromInt(@intFromEnum(map[@intCast(pos.y)][@intCast(pos.x)]) + 1);
+    for (&[_]Coordiates{
+        pos.add(.{ .x = 0, .y = -1 }),
+        pos.add(.{ .x = -1, .y = 0 }),
+        pos.add(.{ .x = 1, .y = 0 }),
+        pos.add(.{ .x = 0, .y = 1 }),
+    }) |other| {
+        if (other.y >= map.len or other.y < 0)
+            continue;
+        const line = &map[@intCast(other.y)];
+        if (other.x >= line.len or other.x < 0)
+            continue;
+        const tile = &line.*[@intCast(other.x)];
+        if (tile.* != expect)
+            continue;
+        if (tile.* == .End) {
+            if (part_1)
+                tile.* = .Empty;
+            result += 1;
+        } else {
+            result += compute(part_1, map, other);
+        }
+    }
+    return result;
+}
+
+fn deinit(array: *std.ArrayList([]HikeTrail)) void {
+    for (array.items) |l| {
+        array.allocator.free(l);
+    }
+    array.deinit();
+}
+
+pub fn solution(alloc: std.mem.Allocator) !utils.AOCSolution {
+    const file = @embedFile("input/day10.txt");
+    var map = try parse_map(alloc, file);
+    defer deinit(&map);
+
+    var sol = utils.AOCSolution{ .part1 = 0, .part2 = 0 };
+    for (0.., map.items) |y, line| {
+        for (0.., line) |x, _| {
+            if (map.items[y][x] == .Start) {
+                var m = try map.clone();
+                defer deinit(&m);
+                for (m.items) |*l| {
+                    l.* = try alloc.dupe(HikeTrail, l.*);
+                }
+                sol.part1 += compute(true, m.items, .{ .x = @intCast(x), .y = @intCast(y) });
+                sol.part2 += compute(false, map.items, .{ .x = @intCast(x), .y = @intCast(y) });
+            }
+        }
+    }
+
+    return sol;
+}
+
+test {
+    const sol = try solution(std.testing.allocator);
+
+    try std.testing.expectEqual(593, sol.part1);
+    try std.testing.expectEqual(1192, sol.part2);
+}

2024/src/input/day10.txt

@@ -0,0 +1,45 @@
+210121012321234586543237650120901076540121001
+101234985490147897890198701221812389430430012
+567105676787458721209877654336765410321569123
+498014785010969630118960165445898923210678234
+309323494323874549823454278321080854100123945
+211234515690123678989923329876571765987637876
+110987601781010501677815410989432894543540345
+021010532782323432596506901098126545652901276
+012123445693437010487417892387087036761892987
+323098530696598923300306103456592123890743210
+014567621787127654211215296503431014125650309
+329643452650034018987894387112321265034321478
+498762167541005329876012379012450996543406567
+567433098932116456705430498763567887456715458
+016526187654327643212321567654654321019823309
+327817656783298984103435433216789670321094215
+438908943090125675678976124105894589452385434
+567617812181034106789780045674583076581276123
+106787801654323295610191230983012109690187012
+245096998745016784327898101092103298781298432
+332165432101565410678765432387654567654382321
+456976541001274328769867211498565650103401450
+697889034012389219654358300567656743212519567
+787765121965476101011249401456549865435658498
+657854320876210894320134562340134678321067019
+548943013456367885012021076543221589801354323
+038765412387478976523256789601100499832231234
+129914302198565985430143898702341300740140145
+878801243089478876943232169219654211655657656
+965760651078769217854321078348778902598748912
+054450782369854308765010127651267143456732103
+123321895451043219678098763410356012349801654
+103456986032112008769123452345441078959798723
+212387872149800123452101011096732163478760810
+301095433458945654343000125687823454307451923
+454346721567238769289210234776916543210312367
+965239810123189378176321349885407892321208498
+870125676034003210065443456790398901765089567
+345676787165612349898652105381210340894176506
+210985696278973656776789965450678256783215410
+101974320161087298785649874367589109891006321
+007876013232196105694234701298432098782107890
+012565434983435234523105650165601105673456921
+323476325876524321012023498074320234504305430
+434789016789012010123110567789210343212214321

2024/src/main.zig

@@ -11,6 +11,7 @@ pub const solutions = [_]?*const fn (std.mem.Allocator) anyerror!utils.AOCSoluti
     @import("day07.zig").solution,
     @import("day08.zig").solution,
     @import("day09.zig").solution,
+    @import("day10.zig").solution,
 };
 
 fn get_day() !?u8 {