/// <summary>
/// This method will calculate the Z-function for the caller string.
/// The result of the Z-function is a vector; the i-th element of this
/// vector is the length of the greatest common prefix of the string with the string SPL,
/// where the SPL is a suffix of the string starting at element i.
/// </summary>
/// <param name="str">The caller string object.</param>
/// <param name="options">The options of searching for the substring.</param>
/// <returns>The Z-function for the string.</returns>
public static int[] calculateZFunction(this string str, SubstringSearchOptions options = SubstringSearchOptions.Default)
{
int length = str.Length;
int[] result = new int[length];
if(length == 0)
return result;
result[0] = str.Length;
int left = 0;
int right = 1;
for (int current = 1; current < length; current++)
{
// Не находится самого правого Z-блока, покрывающего текущий индекс.
// Надо все вычислять с самого начала.
if (current >= right)
{
int offset = 0;
while (current + offset < length && _CHAR_EQUAL(str[current + offset], str[offset], options))
offset++;
result[current] = offset;
left = current;
right = current + offset;
}
// перекрытие есть
else
{
int equivalentIndex = current - left;
// До конца Z-блока осталось больше символов, чем значение Z-функции.
// Можно не проверять.
if (result[equivalentIndex] < right - current)
{
result[current] = result[equivalentIndex];
continue;
}
int offset = 0;
while (right + offset < length && _CHAR_EQUAL(str[right - current + offset], str[right + offset], options))
offset++;
result[current] = right - current + offset;
left = current;
right += offset;
}
}
return result;
}
private static bool _CHAR_EQUAL(char a, char b, SubstringSearchOptions opt)
{
if (opt == SubstringSearchOptions.Default)
return a.Equals(b);
else if (opt == SubstringSearchOptions.CurrentCultureIgnoreCase)
return char.ToLower(a).Equals(char.ToLower(b));
else
return char.ToLowerInvariant(a).Equals(char.ToLowerInvariant(b));
}
/// <summary>
/// Searches for the first occurence of a specified sample string in the calling string
/// using the specified substring search options and returns the index of the occurence or a negative value when unsuccessful.
/// </summary>
/// <param name="str">The calling string object.</param>
/// <param name="sample">The sample string to search for.</param>
/// <param name="options">The options of searching.</param>
/// <returns>The index of the occurence or a negative value when unsuccessful</returns>
public static int indexOfString_ZFunction(this string str, string sample, SubstringSearchOptions options = SubstringSearchOptions.Default)
{
List <int> indices = indicesOfString_ZFunction(str, sample, options);
if (indices.Count > 0)
{
return(indices[0]);
}
else
{
return(-1);
}
}
private static bool _CHAR_EQUAL(char a, char b, SubstringSearchOptions opt)
{
if (opt == SubstringSearchOptions.Default)
{
return(a.Equals(b));
}
else if (opt == SubstringSearchOptions.CurrentCultureIgnoreCase)
{
return(char.ToLower(a).Equals(char.ToLower(b)));
}
else
{
return(char.ToLowerInvariant(a).Equals(char.ToLowerInvariant(b)));
}
}
/// <summary>
/// Searches for all occurences of a specified sample string in the calling string
/// using the specified substring search options and returns the indices of the occurences.
///
/// The indexes of the sample are returned in the form of an int[] array.
/// </summary>
/// <param name="str">The calling string object.</param>
/// <param name="sample">The sample string to search for.</param>
/// <param name="options">The options of searching.</param>
/// <returns>A list of indices in the <paramref name="str"/> where the specified sample string occurs.</returns>
public static List<int> indicesOfString_ZFunction(this string str, string sample, SubstringSearchOptions options = SubstringSearchOptions.Default)
{
string tmp = sample + "\uFFFF" + str;
int[] zFunction = tmp.calculateZFunction(options);
List<int> indices = new List<int>();
for (int i = sample.Length + 1; i < zFunction.Length; i++)
{
if (zFunction[i] == sample.Length)
indices.Add(i - sample.Length - 1);
}
return indices;
}
/// <summary>
/// Searches for the first occurence of a specified sample string in the calling string
/// using the specified substring search options and returns the index of the occurence or a negative value when unsuccessful.
/// </summary>
/// <param name="str">The calling string object.</param>
/// <param name="sample">The sample string to search for.</param>
/// <param name="options">The options of searching.</param>
/// <returns>The index of the occurence or a negative value when unsuccessful</returns>
public static int indexOfString_ZFunction(this string str, string sample, SubstringSearchOptions options = SubstringSearchOptions.Default)
{
List<int> indices = indicesOfString_ZFunction(str, sample, options);
if (indices.Count > 0)
return indices[0];
else
return -1;
}
/// <summary>
/// This method will calculate the Z-function for the caller string.
/// The result of the Z-function is a vector; the i-th element of this
/// vector is the length of the greatest common prefix of the string with the string SPL,
/// where the SPL is a suffix of the string starting at element i.
/// </summary>
/// <param name="str">The caller string object.</param>
/// <param name="options">The options of searching for the substring.</param>
/// <returns>The Z-function for the string.</returns>
public static int[] calculateZFunction(this string str, SubstringSearchOptions options = SubstringSearchOptions.Default)
{
int length = str.Length;
int[] result = new int[length];
if (length == 0)
{
return(result);
}
result[0] = str.Length;
int left = 0;
int right = 1;
for (int current = 1; current < length; current++)
{
// Не находится самого правого Z-блока, покрывающего текущий индекс.
// Надо все вычислять с самого начала.
if (current >= right)
{
int offset = 0;
while (current + offset < length && _CHAR_EQUAL(str[current + offset], str[offset], options))
{
offset++;
}
result[current] = offset;
left = current;
right = current + offset;
}
// перекрытие есть
else
{
int equivalentIndex = current - left;
// До конца Z-блока осталось больше символов, чем значение Z-функции.
// Можно не проверять.
if (result[equivalentIndex] < right - current)
{
result[current] = result[equivalentIndex];
continue;
}
int offset = 0;
while (right + offset < length && _CHAR_EQUAL(str[right - current + offset], str[right + offset], options))
{
offset++;
}
result[current] = right - current + offset;
left = current;
right += offset;
}
}
return(result);
}
/// <summary>
/// Searches for all occurences of a specified sample string in the calling string
/// using the specified substring search options and returns the indices of the occurences.
///
/// The indexes of the sample are returned in the form of an int[] array.
/// </summary>
/// <param name="str">The calling string object.</param>
/// <param name="sample">The sample string to search for.</param>
/// <param name="options">The options of searching.</param>
/// <returns>A list of indices in the <paramref name="str"/> where the specified sample string occurs.</returns>
public static List <int> indicesOfString_ZFunction(this string str, string sample, SubstringSearchOptions options = SubstringSearchOptions.Default)
{
string tmp = sample + "\uFFFF" + str;
int[] zFunction = tmp.calculateZFunction(options);
List <int> indices = new List <int>();
for (int i = sample.Length + 1; i < zFunction.Length; i++)
{
if (zFunction[i] == sample.Length)
{
indices.Add(i - sample.Length - 1);
}
}
return(indices);
}
