56 lines
1.5 KiB
Zig
56 lines
1.5 KiB
Zig
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const std = @import("std");
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pub fn main() !void {
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var gpa = std.heap.GeneralPurposeAllocator(.{}){};
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const allocator = gpa.allocator();
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defer _ = gpa.deinit();
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const stdin = std.io.getStdIn();
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var buf_io = std.io.bufferedReader(stdin.reader());
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var reader = buf_io.reader();
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const text = try reader.readAllAlloc(allocator, 100000);
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defer allocator.free(text);
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std.debug.print("{}", .{try visit(allocator, text)});
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}
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fn visit(allocator: std.mem.Allocator, seq: []const u8) !u32 {
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var visited = std.AutoHashMap([2]i32, void).init(allocator);
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defer visited.deinit();
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var santa: [2]i32 = .{ 0, 0 };
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var robosanta: [2]i32 = .{ 0, 0 };
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// Set origin as visited
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try visited.put(santa, {});
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for (0.., seq) |i, c| {
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if (i % 2 == 0) {
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santa = move(santa, c);
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try visited.put(santa, {});
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} else {
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robosanta = move(robosanta, c);
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try visited.put(robosanta, {});
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}
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}
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return visited.count();
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}
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fn move(current: [2]i32, c: u8) [2]i32 {
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return switch (c) {
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'>' => .{ current[0] + 1, current[1] },
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'<' => .{ current[0] - 1, current[1] },
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'^' => .{ current[0], current[1] + 1 },
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'v' => .{ current[0], current[1] - 1 },
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else => current,
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};
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}
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test "day-tests" {
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try std.testing.expectEqual(try visit(std.testing.allocator, "^v"), 3);
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try std.testing.expectEqual(try visit(std.testing.allocator, "^>v<"), 3);
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try std.testing.expectEqual(try visit(std.testing.allocator, "^v^v^v^v^v"), 11);
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}
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