Department numbers: Difference between revisions

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Using a Zig ''struct'' to create an iterator is a common pattern in Zig.

<syntaxhighlight lang="zig"~~>const std = @import("std");</syntaxhighlight~~>

const std = @import("std");

~~<syntaxhighlight lang="zig">~~pub fn main() !void {

pub fn main() !void {

const stdout = std.io.getStdOut().writer();

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try stdout.writeAll("------ ---------- ----\n");

var it = SolutionIterator{};

var it = SolutionIterator.init();

while (it.next()) |solution| {

try stdout.print(

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const SolutionIterator = struct {

// police initialized to ~~zero~~ as adding one is the first operation ~~for~~ next()

// police is initialized to one as adding one is the first operation in next()

// with the result .police == 2 (an even number) on the first pass.

u: DepartmentsUnion = .{ .departments = .{ .police = 0, .sanitation = 1, .fire = 1 } },

u: DepartmentsUnion = .{ .departments = .{ .police = 1, .sanitation = 1, .fire = 1 } },

/// init() returns an initialised structure.

/// Using init() is a common Zig pattern.

fn init() SolutionIterator {

return SolutionIterator{};

}

fn next(self: *SolutionIterator) ?Departments {

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if (self.u.departments.sanitation == self.u.departments.fire) continue;

if (self.u.departments.fire == self.u.departments.police) continue;

// Must ~~equal~~ twelve (maximum sum 6 + 7 + 7 = 20 requires 5 bits)

// Must total twelve (maximum sum 7 + 7 + 7 = 21 requires 5 bits)

const p = @as(u5, self.u.departments.police);

const s = @as(u5, self.u.departments.sanitation);