/// <summary>
/// Finds all the occurences a pattern in a a string
/// </summary>
/// <param name="pattern">The pattern to search for</param>
/// <param name="targetString">The target string to search for</param>
/// <returns>
/// Return an Arraylist containing the indexs where the
/// patternn occured
/// </returns>
private static ArrayList GetOccurences(string pattern, string targetString)
{
ArrayList result;
int[] transitionArray;
char[] charArray;
char[] patternArray;
charArray = targetString.ToLower().ToCharArray();
patternArray = pattern.ToLower().ToCharArray();
result = new ArrayList();
PrefixArray prefixArray = new PrefixArray(pattern);
transitionArray = prefixArray.TransitionArray;
//Keeps track of the pattern index
int k = 0;
for (int i = 0; i < charArray.Length; i++)
{
//If there is a match
if (charArray[i] == patternArray[k])
{
//Move the pattern index by one
k++;
}
else
{
//There is a mismatch..so move the pattern
//The amount to move through the pattern
int prefix = transitionArray[k];
//if the current char does not match
//the char in the pattern that concides
//when moved then shift the pattern entirley, so
//we dont make a unnecssary comparision
if (prefix + 1 > patternArray.Length &&
charArray[i] != patternArray[prefix + 1])
{
k = 0;
}
else
{
k = prefix;
}
}
//A complet match, if kis
//equal to pattern length
if (k == patternArray.Length)
{
//Add it to our result
result.Add(i - (patternArray.Length - 1));
//Set k as if the next character is a mismatch
//therefore we dont mis out any other containing
//pattern
k = transitionArray[k - 1];
}
}
return(result);
}
