Files used for the free book contest

README.md

Book Draw

This is the code used to decide the winner of the draw for a free copy of my book "Android for iOS Developers" on March 24th, 2017, as announced on Twitter.

Requirements

This C++ program has been tested on macOS Sierra 10.12.3 with the latest Xcode developer tools, Homebrew and CMake. You can install CMake using Homebrew:

brew install cmake

Build and Run

Copy the files CMakeLists.txt and main.cpp into a folder, cd into that folder and type the following commands:

cmake .
make
./bookdraw

Winner

The draw is available in asciinema, and the winner is @yostane!

CMakeLists.txt

cmake_minimum_required(VERSION 3.6)
project(bookdraw)

set(CMAKE_CXX_STANDARD 14)

set(SOURCE_FILES main.cpp)
add_executable(bookdraw ${SOURCE_FILES})

main.cpp

#include <iostream>
#include <random>
#include <sstream>

using namespace std;

using Players = vector<string>;

int main() {
    Players players{"@0xced", "@GuickPa", "@HerveCaumont", "@LakaLe_", "@MarcioK",
                    "@Neilkachu", "@VijayTholpadi", "@a_schacherbauer", "@agisilaosts",
                    "@apouche", "@azouts", "@dmytrolisitsyn", "@draufunddran1", "@ge_hn",
                    "@guiiipontes", "@igorescobar", "@ikarius", "@jadekin",
                    "@janiskirsteins", "@jolyAlexandre", "@kedarv", "@kyegeorge",
                    "@leakywellington", "@lipec", "@m_sgr_bot", "@marius_const",
                    "@onmyway133", "@ooswald", "@paulrikmans", "@pbendersky",
                    "@relausen", "@rpresedo", "@rshankra", "@sandeepCool77", "@sconig",
                    "@whakkee", "@xmonodev", "@xrb", "@yostane", "@zen_prog"};

    auto shuffle = [](Players &p) -> void {
        auto seed = chrono::system_clock::now().time_since_epoch().count();
        std::shuffle(p.begin(), p.end(), default_random_engine(seed));
    };

    auto stats = [](Players &p) -> string {

        auto join = [p](string separator) -> string {
            ostringstream stream;
            auto iterator = ostream_iterator<string>(stream, separator.c_str());
            copy(p.begin(), p.end(), iterator);
            auto str = stream.str();
            str.erase(str.length() - separator.size());
            return str;
        };

        stringstream stream;
        stream << p.size() << " players: " << join(", ");
        return stream.str();
    };

    auto congrats = [](string &winner, uint32_t number) -> string {
        string medal{"\U0001F3C5"};
        string cup{"\U0001F3C6"};
        string gift{"\U0001F381"};
        string thumbsup{"\U0001F44D"};
        stringstream stream;
        stream << "And the winner is…  " << medal << "  " << cup
               << "  ~~ " << winner << " ~~  "
               << gift << "  " << thumbsup << "  (number " << number << ")";
        return stream.str();
    };

    auto draw = [shuffle](Players &p) {
        auto times = arc4random_uniform(1000);
        uint32_t lottery;
        string winner;
        for (int i = 0; i < times; ++i) {
            shuffle(p);
            lottery = arc4random_uniform(p.size());
            winner = p[lottery];
        }
        return make_pair(lottery, winner);
    };

    auto result = draw(players);
    auto lottery = result.first;
    auto winner = result.second;

    cout << stats(players) << endl;
    cout << endl;
    cout << congrats(winner, lottery) << endl;
    cout << endl;
    return 0;
}