const std = @import("std");
const INPUT = "394618527";
const Str = []const u8;
pub fn first(allocator: ?std.mem.Allocator) anyerror!usize {
    var cc = try parseInput(allocator.?, INPUT);
    defer {
        cc.cups.deinit();
    }
    var round: usize = 0;
    while (round < 100) : (round += 1) {
        // std.debug.print("{d} {any}\n", .{ cc.current, cc.cups.items });
        try cc.move(allocator.?);
    }
    var ret: usize = 0;
    const one = std.mem.indexOf(CupType, cc.cups.items, &[_]CupType{1}).?;
    var idx: usize = 0;
    while (idx < 8) : (idx += 1) {
        ret += cc.cups.items[(one + idx + 1) % cc.cups.items.len] *
            try std.math.powi(usize, 10, cc.cups.items.len - idx - 2);
    }
    return ret;
}
pub fn second(allocator: ?std.mem.Allocator) anyerror!usize {
    _ = allocator;
    return 0;
}
const CupType = u4;
const Cups = std.ArrayList(CupType);
const CrabCups = struct {
    cups: Cups = undefined,
    fn move(self: *@This(), allocator: std.mem.Allocator) !void {
        const cup1 = self.cups.orderedRemove(1);
        const cup2 = self.cups.orderedRemove(1);
        const cup3 = self.cups.orderedRemove(1);
        // std.debug.print("pick up: {d} {d} {d}\n", .{ cup1, cup2, cup3 });
        const destination = blk: {
            var dest: CupType = self.cups.items[0];
            while (true) : (dest -= 1) {
                if (dest == 0) dest = 9;
                if (dest != self.cups.items[0] and dest != cup1 and dest != cup2 and dest != cup3) {
                    break;
                }
            }
            break :blk dest;
        };
        // std.debug.print("destination: {}\n", .{destination});
        const dest_index = std.mem.indexOf(CupType, self.cups.items, &[_]CupType{destination}).?;
        try self.cups.insertSlice((dest_index + 1) % 9, &[_]CupType{ cup1, cup2, cup3 });
        var next = try Cups.initCapacity(allocator, self.cups.items.len);
        for ([_]usize{ 1, 2, 3, 4, 5, 6, 7, 8, 9 }) |offset| {
            next.appendAssumeCapacity(self.cups.items[offset % self.cups.items.len]);
        }
        self.cups.deinit();
        self.cups = next;
    }
};
fn parseInput(allocator: std.mem.Allocator, input: Str) anyerror!CrabCups {
    var ret: CrabCups = undefined;
    ret.cups = try std.ArrayList(CupType).initCapacity(allocator, 9);
    for (input) |_, idx| {
        const cup = try std.fmt.parseUnsigned(CupType, input[idx .. idx + 1], 10);
        ret.cups.appendAssumeCapacity(cup);
    }
    return ret;
}
test "day23a" {
    try std.testing.expectEqual(@as(usize, 78569234), try first(std.testing.allocator));
}
test "day23b" {
    try std.testing.expectEqual(@as(usize, 0), try second(std.testing.allocator));
}
const test_input = "389125467";