/// <summary>
/// Find an estimated length and use regular binary search
/// <para>Time Complexity: O(log(n))</para>
/// <para>Space Complexity: O(log(n)) - recursion depth</para>
/// </summary>
/// <param name="list"></param>
/// <param name="item"></param>
/// <returns></returns>
public static int SearchWithNoSize(Listy list, int item)
{
if (list == null)
{
return(-1);
}
// Find length - runtime O(log(n))
int index = 1;
while (list.ElementAt(index) != -1 && list.ElementAt(index) < item)
{
index *= 2;
}
return(Search(list, item, index / 2, index));
}
private static int Search(Listy list, int item, int start, int end)
{
if (start > end)
{
return(-1);
}
int mid = (start + end) / 2;
if (list.ElementAt(mid) == item)
{
return(mid);
}
else if (list.ElementAt(mid) > item || list.ElementAt(mid) == -1)
{
return(Search(list, item, start, mid - 1));
}
else
{
return(Search(list, item, mid + 1, end));
}
}
//10.4 Sorted Search, No Size: You are given an array like data structure Listy which lacks a size
// method. It does, however, have an elementAt ( i) method that returns the element at index i in
// 0( 1) time. If i is beyond the bounds of the data structure, it returns -1. (For this reason, the data
// structure only supports positive integers.) Given a Li sty which contains sorted, positive integers,
// find the index at which an element x occurs. If x occurs multiple times, you may return any index.
public static int Search(Listy list, int value)
{
int index = 1;
while (list.ElementAt(index) != -1 && list.ElementAt(index) < value)
{
index *= 2;
}
return(BinarySearch(index / 2, index));
int BinarySearch(int low, int high)
{
int mid;
while (low <= high)
{
mid = (low + high) / 2;
int middle = list.ElementAt(mid);
if (middle > value && middle == -1)
{
high = mid - 1;
}
else if (middle < value)
{
low = mid + 1;
}
else
{
return(mid);
}
}
return(-1);
}
}
/// <summary>
/// Searches an array-like data structure that has no size method or property
/// </summary>
/// <param name="list"></param>
/// <param name="key"></param>
/// <returns></returns>
public static int SearchListy(Listy <int> list, int key)
{
if (list == null || list.ElementAt(0) == -1)
{
return(-1);
}
int index = 1;
while (list.ElementAt(index) != -1 && list.ElementAt(index) < key)
{
index *= 2;
}
int low = index / 2;
int high = index;
while (low < high)
{
int mid = (low + high) / 2;
if (list.ElementAt(mid) == key)
{
return(mid);
}
else if (list.ElementAt(mid) == -1)
{
high = mid - 1;
}
else if (list.ElementAt(mid) < key)
{
low = mid + 1;
}
else if (list.ElementAt(mid) > key)
{
high = mid - 1;
}
}
return(-1);
}
