62 lines
2.1 KiB
Zig
62 lines
2.1 KiB
Zig
const std = @import("std");
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const example = @embedFile("example");
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const input = @embedFile("input");
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pub fn main() anyerror!void {
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var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
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defer arena.deinit();
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const allocator = arena.allocator();
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var output = try solve(example, allocator);
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try std.testing.expect(std.mem.eql(u8, output, "CMZ"));
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const result = try solve(input, allocator);
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try std.io.getStdOut().writer().print("{s}\n", .{result});
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}
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fn solve(puzzle: []const u8, allocator: std.mem.Allocator) ![]u8 {
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var it = std.mem.tokenize(u8, puzzle, "\n");
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var line = it.next() orelse unreachable;
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// Initializations from the first line
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const size = (line.len + 1) / 4;
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var output = try allocator.alloc(u8, size);
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var stacks = try allocator.alloc(std.ArrayList(u8), size);
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for (stacks) |*stack| {
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stack.* = std.ArrayList(u8).init(allocator);
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}
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// parse stacks
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while (true) {
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var i: usize = 0;
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while (i < size) : (i += 1) {
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const v = line[i * 4 + 1];
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if (v != ' ') {
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try stacks[i].insert(0, v);
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}
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}
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line = it.next() orelse unreachable;
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if (line[0] != '[') { // we got the line with numbers
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break;
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}
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}
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// process rules
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while (it.next()) |l| {
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var elts = std.mem.split(u8, l, " ");
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_ = elts.next() orelse unreachable; // the move word
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var n = try std.fmt.parseInt(u8, elts.next() orelse unreachable, 10);
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_ = elts.next() orelse unreachable; // the from word
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const s = try std.fmt.parseInt(u8, elts.next() orelse unreachable, 10) - 1;
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_ = elts.next() orelse unreachable; // the to word
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const d = try std.fmt.parseInt(u8, elts.next() orelse unreachable, 10) - 1;
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while (n > 0) : (n -= 1) {
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const v = stacks[s].pop();
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try stacks[d].append(v);
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}
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}
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// generate output
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var i: usize = 0;
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while (i < size) : (i += 1) {
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output[i] = stacks[i].pop();
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}
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return output;
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}
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