ComputerSecurity/firstcw/cw3-alt/src/main.zig

const std = @import("std");

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

fn print(comptime str: []const u8, args: anytype) void {
    stdout.print(str, args) catch unreachable;
}

fn println(comptime str: []const u8, args: anytype) void {
    print(str ++ "\n", args);
}

//const n: u512 = 7405872386298001828045412304885395957447735855540402226273272018863616985100578690399814241980651881616439657049448993379923363875365701026162288146836853;

const n: u512 = 70666344586694209770041979947;
//const n: u512 = 77;

var sqrt: u512 = undefined;

fn base3Mask(val: u512, size: usize) u512 {
    return val % std.math.pow(u512, 10, size);
}

var nBase: []u512 = undefined;

pub fn main() !void {
    var alloctor = std.heap.ArenaAllocator.init(std.heap.page_allocator);
    defer alloctor.deinit();

    var alloc = alloctor.allocator();

    var size_n: usize = std.math.log10_int(n) + 2;

    nBase = try alloc.alloc(u512, size_n);

    for (0..size_n) |i| {
        nBase[i] = base3Mask(n, i + 1);
    }

    searchPackAccStart(1);
}

fn searchPackAccStart(acc: u64) void {
    for (0..10) |_i| {
        var i: u512 = _i;
        for (0..10) |_j| {
            var j: u512 = _j;
            var mul: u512 = i * j;
            if (mul == n) {
                println("Found them {} {}!", .{ j, i });
                std.os.exit(1);
            }
            if (mul > n) break;
            var mulMask = base3Mask(mul, acc);

            if (mulMask == nBase[acc - 1]) {
                searchPackAcc(acc + 1, i, j, 10, 10);
            }
        }
    }
}

fn searchPackAcc(acc: u64, n1: u512, n2: u512, _size_n1: u512, _size_n2: u512) void {
    var size_n1 = _size_n1;
    var size_n2 = _size_n2;
    for (0..10) |_i| {
        var i = _i * _size_n1 + n1;
        size_n2 = _size_n2;
        for (0..10) |_j| {
            var j = _j * _size_n2 + n2;
            var mul: u512 = i * j;
            if (mul > n) break;
            if (mul == n) {
                if (i == 1 or j == 1) {
                    break;
                }
                println("Found them {} {}!", .{ j, i });
                std.os.exit(1);
            }
            var mulMask = base3Mask(mul, acc);

            if (mulMask == nBase[acc - 1]) {
                println("trying {} {}-{}({}) {}-{}({}) {}", .{ acc, _i, i, _size_n1, _j, j, _size_n2, mul });
                searchPackAcc(acc + 1, i, j, size_n1, size_n2);
            }
            if (_j == 0) {
                size_n2 *= 10;
            }
        }
        if (_i == 0) {
            size_n1 *= 10;
        }
    }
}