CODEWITHSUNDEEP
c#.net
wrum wrum
wrum wrum

Reputation: 13

Can someone explain me why it throws an ArgumentOutOfRangeException?

static List<object> JosephusPermutation(List<object> items, int k)
{
  List<object> solution = new List<object>();
  int index = k - 1;
  int len = items.Count;
  int count = 1;
  foreach(object i in items){
    if(index<len){
      solution.Add(items[index]);
      index += k;
    }
    else{
      index = (index - 1) - len * count;
      count++;
    }
  }
  return solution;
}

I tried to create a function that takes every k element in the array and get an OutOfRangeException and don't know why it's happening. Can you explain me why these piece of code behaves like these? Appreciate your help!

Upvotes: 1

Views: 98

Answers (1)

carlfriedrich
carlfriedrich

Reputation: 4113

This line is the reason:

index = (index - 1) - len * count;

As soon as count is > 1, you're substracting a number bigger than the list length, resulting in a negative index. Removing the * count should fix this.

Upvotes: 1

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