Silly solutions to elementary problems

Occasionally people share entertainingly bad solutions to basic programming interview questions. In that same spirit, I dump some compositions here.

Checking whether a number is even by using C strings

bool isEven(int n) {
    char a[30];
    sprintf(a, "%d", ((n >> 1) << 1) - n);
    sprintf(a + strlen(a) + 1, "%d", n - ((n >> 1) << 1));
    return strlen(a + strlen(a) + 1) + 1 > strlen(a);
}

Checking whether a number is even by using AI data annotation

using System.Windows.Forms;
bool IsEven(int n)
    => DialogResult.Yes ==  MessageBox.Show($"Is {n} even?", default, MessageBoxButtons.YesNo, default, default, default, default, default);

Checking whether a number is even by using automated theorem proving

using Microsoft.Z3;
bool IsEven(int value) {
    using var ctx = new Context();
    var n = ctx.MkIntConst("n");
    var solver = ctx.MkSolver();
    solver.Assert(ctx.MkEq(ctx.MkInt(value), n));
    solver.Assert(ctx.MkEq(n, ctx.MkMul(ctx.MkIntConst("k"), ctx.MkInt(2))));
    return solver.Check() == Status.SATISFIABLE;
}

Checking whether a number is even by using a graph

class LinkedListNode<T> {
    public T Value { get; set; }
    public LinkedListNode<T> Next { get; set; }
}

static LinkedListNode<bool> MakeCycle(int length) {
    var first = new LinkedListNode<bool> { Value = true };
    var current = first;
    for (int i = 1; i < length; ++i) {
        var next = new LinkedListNode<bool> { Value = false };
        current.Next = next;
        current = next;
    }

    current.Next = first;
    return first;
}

public static bool IsEven(int n) {
    var current = MakeCycle(2);
    if (n < 0)
        n = -n;
    while (n --> 0)
        current = current.Next;

    return current.Value;
}

Checking who won in a game of rock-paper-scissors by using bitwise rotation

enum Choice {
    Rock = 1,
    Paper = 2,
    Scissors = 4
};

enum Outcome {
    Tie, FirstWins, SecondWins
};

Outcome getOutcome(Choice first, Choice second)
{
    if (first == second)
        return Outcome::Tie;
    if (((first >> 1 | first << 2) & 7) == second)
        return Outcome::FirstWins;
    return Outcome::SecondWins;
}