aboutsummaryrefslogtreecommitdiff
path: root/2022/05-supply-stacks/second.zig
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--2022/05-supply-stacks/second.zig61
1 files changed, 61 insertions, 0 deletions
diff --git a/2022/05-supply-stacks/second.zig b/2022/05-supply-stacks/second.zig
new file mode 100644
index 0000000..580f69b
--- /dev/null
+++ b/2022/05-supply-stacks/second.zig
@@ -0,0 +1,61 @@
+const std = @import("std");
+
+const example = @embedFile("example");
+const input = @embedFile("input");
+
+pub fn main() anyerror!void {
+ var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+ defer arena.deinit();
+ const allocator = arena.allocator();
+
+ var output = try solve(example, allocator);
+ try std.testing.expect(std.mem.eql(u8, output, "MCD"));
+
+ const result = try solve(input, allocator);
+ try std.io.getStdOut().writer().print("{s}\n", .{result});
+}
+
+fn solve(puzzle: []const u8, allocator: std.mem.Allocator) ![]u8 {
+ var it = std.mem.tokenize(u8, puzzle, "\n");
+ var line = it.next() orelse unreachable;
+ // Initializations from the first line
+ const size = (line.len + 1) / 4;
+ var output = try allocator.alloc(u8, size);
+ var stacks = try allocator.alloc(std.ArrayList(u8), size);
+ for (stacks) |*stack| {
+ stack.* = std.ArrayList(u8).init(allocator);
+ }
+ // parse stacks
+ while (true) {
+ var i: usize = 0;
+ while (i < size) : (i += 1) {
+ const v = line[i * 4 + 1];
+ if (v != ' ') {
+ try stacks[i].insert(0, v);
+ }
+ }
+ line = it.next() orelse unreachable;
+ if (line[0] != '[') { // we got the line with numbers
+ break;
+ }
+ }
+ // process rules
+ while (it.next()) |l| {
+ var elts = std.mem.split(u8, l, " ");
+ _ = elts.next() orelse unreachable; // the move word
+ var n = try std.fmt.parseInt(u8, elts.next() orelse unreachable, 10);
+ _ = elts.next() orelse unreachable; // the from word
+ const s = try std.fmt.parseInt(u8, elts.next() orelse unreachable, 10) - 1;
+ _ = elts.next() orelse unreachable; // the to word
+ const d = try std.fmt.parseInt(u8, elts.next() orelse unreachable, 10) - 1;
+ const nl = stacks[s].items.len - n;
+ try stacks[d].appendSlice(stacks[s].items[nl..]);
+ stacks[s].items.len = nl;
+ }
+ // generate output
+ var i: usize = 0;
+ while (i < size) : (i += 1) {
+ output[i] = stacks[i].pop();
+ }
+ return output;
+}