Day7

day7/zig/main.zig

@@ -0,0 +1,107 @@
+const std = @import("std");
+
+const Tile = enum {
+    start,
+    empty,
+    splitter,
+};
+
+pub fn main() !void {
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    defer _ = gpa.deinit();
+
+    var stdin_buffer: [4096]u8 = undefined;
+    var stdin_reader = std.fs.File.stdin().reader(&stdin_buffer);
+
+    const stdin = &stdin_reader.interface;
+
+    const allocator = gpa.allocator();
+    var map = try std.ArrayList(std.ArrayList(Tile)).initCapacity(allocator, 1);
+    defer map.deinit(allocator);
+
+    while (try stdin.takeDelimiter('\n')) |line| {
+        var row = try std.ArrayList(Tile).initCapacity(allocator, 1);
+
+        for (line) |char| {
+            switch (char) {
+                'S' => {
+                    try row.append(allocator, Tile.start);
+                },
+                '.' => {
+                    try row.append(allocator, Tile.empty);
+                },
+                '^' => {
+                    try row.append(allocator, Tile.splitter);
+                },
+                else => unreachable,
+            }
+        }
+
+        try map.append(allocator, row);
+    }
+
+    var start_x: usize = 0;
+    for (map.items[0].items, 0..) |tile, i| {
+        if (tile == Tile.start) {
+            start_x = i;
+            break;
+        }
+    }
+
+    var beammap = try std.ArrayList(std.ArrayList(u64)).initCapacity(allocator, 1);
+    defer beammap.deinit(allocator);
+
+    for (0..map.items.len) |_| {
+        var row = try std.ArrayList(u64).initCapacity(allocator, 1);
+
+        for (0..map.items[0].items.len) |_| {
+            try row.append(allocator, 0);
+        }
+
+        try beammap.append(allocator, row);
+    }
+
+    beammap.items[0].items[start_x] = 1;
+
+    var task1: u32 = 0;
+
+    for (beammap.items, 0..) |beamrow, i| {
+        for (beamrow.items, 0..) |has_beam, j| {
+            if (has_beam > 0 and map.items[i].items[j] == Tile.splitter) {
+                if (j != 0) {
+                    beammap.items[i].items[j - 1] += beammap.items[i].items[j];
+                }
+                if (j < beamrow.items.len - 1) {
+                    beammap.items[i].items[j + 1] += beammap.items[i].items[j];
+                }
+                beammap.items[i].items[j] = 0;
+                task1 += 1;
+            }
+        }
+
+        // Copy beams to next row
+        if (i == beammap.items.len - 1) {
+            continue;
+        }
+
+        for (0..beamrow.items.len) |j| {
+            beammap.items[i + 1].items[j] = beammap.items[i].items[j];
+        }
+    }
+
+    var task2: u64 = 0;
+    for (beammap.items[beammap.items.len - 1].items) |n| {
+        task2 += n;
+    }
+
+    std.debug.print("{d}\n", .{task1});
+    std.debug.print("{d}\n", .{task2});
+
+    for (map.items) |*row| {
+        row.deinit(allocator);
+    }
+
+    for (beammap.items) |*row| {
+        row.deinit(allocator);
+    }
+}