I have the code for the josephus problem using recursion but I don't quite understand it can some one explain to me

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you can see the josephus problem at Josephus problem - Wikipedia[^] and i already know the solution that doesn't use recursion but i really want to know how this one works. in this case i'm using the step 2 which means when it deletes n(a number) then it jumps n+1 and then deletes n+2.

What I have tried:

C++

<pre>
#include <stdio.h>
#include <stdlib.h>
int winner(int n){
if (n==1)
    return 1;
else
    return (winner(n-1)+1)%n+1;
}
int main()
{
    int n;
    scanf("%d", &n);
printf("%d", winner(n));
    return 0;
}

Posted 17-Nov-18 5:23am

average_angela

Updated 17-Nov-18 5:58am

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OriginalGriff · Accepted Answer · 2018-11-17T05:59:00

What's to explain? Either you understand recursion, or you need to learn it.
To learn recursion is simple to do: just learn recursion.

The winner method is called with a specific value for n. If it isn't one (i.e. the winning position) it calls itself with n minus one, and uses the result from that to calculate teh winning position.
If you understand how recursion works, it's pretty clear.

So grab the debugger, and follow the code through. It's worth making a quick change first. Change this:

return (winner(n-1)+1)%n+1;

to this:

{
int res = winner(n-1);
res = res + 1;
res = res % n + 1;
return res;
}

That way, you can follow exactly what is being done (and returned) at each stage.