JosephusProblem.cs

usingSystem;

namespaceAlgorithms.Numeric;

publicstaticclassJosephusProblem
{
/// <summary>
/// Calculates the winner in the Josephus problem.
/// </summary>
/// <param name="n">The number of people in the initial circle.</param>
/// <param name="k">The count of each step. k-1 people are skipped and the k-th is executed.</param>
/// <returns>The 1-indexed position where the player must choose in order to win the game.</returns>
publicstaticlongFindWinner(longn,longk)
{
if(k<=0)
{
thrownewArgumentException("The step cannot be smaller than 1");
}

if(k>n)
{
thrownewArgumentException("The step cannot be greater than the size of the group");
}

longwinner=0;
for(longstepIndex=1;stepIndex<=n;++stepIndex)
{
winner=(winner+k)%stepIndex;
}

returnwinner+1;
}
}