/// <summary>
/// Search for value in listy.
/// </summary>
/// <param name="listy">The list.</param>
/// <param name="value">The value to find.</param>
/// <returns>The index of the value or -1 if not found.</returns>
public static int Search(Listy listy, int value)
{
// Error checking.
if (listy == null)
{
throw new ArgumentException("Both arrays must be non-null");
}
// Error checking.
if (value < 0)
{
throw new ArgumentException("Value must be positive.");
}
var index = 0;
var element = listy.ElementAt(index);
while (element < value && element != -1)
{
index++;
element = listy.ElementAt(index);
}
if (element == -1)
{
return(-1);
}
else
{
return(index);
}
}
/// <summary>
/// Search for value in listy.
/// </summary>
/// <param name="listy">The list.</param>
/// <param name="value">The value to find.</param>
/// <returns>The index of the value or -1 if not found.</returns>
public static int Search(Listy listy, int value)
{
// Error checking.
if (listy == null)
{
throw new ArgumentException("Both arrays must be non-null");
}
// Error checking.
if (value < 0)
{
throw new ArgumentException("Value must be positive.");
}
// Find starting index.
var index = 1;
var element = listy.ElementAt(index);
while (element != -1 && element < value)
{
index *= 2;
element = listy.ElementAt(index);
}
// Initialize indexes.
var indexStart = index / 2;
var indexEnd = index;
// At this point we know that value is between indexStart and indexEnd.
// Do a standard binary search.
while (indexEnd >= indexStart)
{
// Get middle element.
var middle = ((indexEnd - indexStart) / 2) + indexStart;
element = listy.ElementAt(middle);
// Go left.
if (element == -1 || value < element)
{
indexEnd = middle - 1;
}
else if (value > element)
// Go right.
{
indexStart = middle + 1;
}
// Match.
else
{
return(middle);
}
}
// Not found.
return(-1);
}
/// <summary>
/// Search for value in listy.
/// </summary>
/// <param name="listy">The list.</param>
/// <param name="value">The value to find.</param>
/// <returns>The index of the value or -1 if not found.</returns>
public static int Search(Listy listy, int value)
{
// Error checking.
if (listy == null)
{
throw new ArgumentException("Both arrays must be non-null");
}
// Error checking.
if (value < 0)
{
throw new ArgumentException("Value must be positive.");
}
// Note: Important that index starts at zero to handle case where
// matching element is first element in array.
var indexPrev = 0;
var index = 0;
int?indexLast = null;
// Outer loop, unknown length binary search.
// Note: End point is
// indexPrev == indexLast (First element is element we are looking for)
// or indexPrev == indexLast - 1 (Element not found).
while (indexLast == null || (indexPrev < indexLast - 1))
{
// Start increment at 1.
var indexIncrement = 1;
// Get current element.
var element = listy.ElementAt(index);
// Inner loop find element or outside of array bounds.
while (element != -1 && element < value)
{
// Store previous index.
indexPrev = index;
// Update the index and element.
index += indexIncrement;
element = listy.ElementAt(index);
// Update the increment.
indexIncrement *= 2;
}
// Found element.
if (element == value)
{
return(index);
}
// Store last index.
indexLast = index;
// Reset starting location.
index = indexPrev;
}
// Not found.
return(-1);
}