interview question answers continued

Another Interview question is how do you find an integer in a circularly sorted integers, then tell how will you find an integer.
In this case there is one factor working for us - which is that the integer collection is sorted and the another that we could choose to ignore if we knew the length of the array.  A circular array index is bounded by the modulo length.  We can confirm if the array is circular if the link and skip level link meet at the same node.
Starting with any position, the integers in one direction are monotonically increasing or decreasing in nature and in the other direction may or may not be so.  So you start with the first and last index positions, find the mid point and look in either half in each iteration, update the start and end to select a half until a find or if start and end cross over.

public int FindSorted(int[] input, int val)
{
int start = 0;
int end = input.Length - 1;
while (start < end)
{
int mid = start + (end - start) / 2;
if (input[mid] == val) return mid;
if (input[start] <= input [mid])
{
if ( input[start] <= val && val < input[mid])
end = mid - 1;
else
start = mid + 1;
}
else
{
if (input[mid] < val && val <= input[end])
start = mid + 1;
else
end = mid - 1;
}
}

if (input[start] == val) return start;

if (input[end] == val) return end;
return -1;
}