public void Build_2()
{
List <int> longestProperPrefixes1 = LLPPS.Build("abcdef");
Assert.AreEqual(0, longestProperPrefixes1[0]);
Assert.AreEqual(0, longestProperPrefixes1[1]);
Assert.AreEqual(0, longestProperPrefixes1[2]);
Assert.AreEqual(0, longestProperPrefixes1[3]);
Assert.AreEqual(0, longestProperPrefixes1[4]);
Assert.AreEqual(0, longestProperPrefixes1[5]);
}
public void Build_1()
{
List <int> longestProperPrefixes1 = LLPPS.Build("aaaabcbaab");
Assert.AreEqual(0, longestProperPrefixes1[0]);
Assert.AreEqual(1, longestProperPrefixes1[1]);
Assert.AreEqual(2, longestProperPrefixes1[2]);
Assert.AreEqual(3, longestProperPrefixes1[3]);
Assert.AreEqual(0, longestProperPrefixes1[4]);
Assert.AreEqual(0, longestProperPrefixes1[5]);
Assert.AreEqual(0, longestProperPrefixes1[6]);
Assert.AreEqual(1, longestProperPrefixes1[7]);
Assert.AreEqual(2, longestProperPrefixes1[8]);
Assert.AreEqual(0, longestProperPrefixes1[9]);
}
public void Build_3()
{
List <int> longestProperPrefixes1 = LLPPS.Build("ddgddcddgdd");
Assert.AreEqual(0, longestProperPrefixes1[0]);
Assert.AreEqual(1, longestProperPrefixes1[1]);
Assert.AreEqual(0, longestProperPrefixes1[2]);
Assert.AreEqual(1, longestProperPrefixes1[3]);
Assert.AreEqual(2, longestProperPrefixes1[4]);
Assert.AreEqual(0, longestProperPrefixes1[5]);
Assert.AreEqual(1, longestProperPrefixes1[6]);
Assert.AreEqual(2, longestProperPrefixes1[7]);
Assert.AreEqual(3, longestProperPrefixes1[8]);
Assert.AreEqual(4, longestProperPrefixes1[9]);
Assert.AreEqual(5, longestProperPrefixes1[10]);
}
public static List <int> Search(string text, string pattern)
{
/* Starts with a preprocessing step. Get the data structure for longest proper prefix that is also a suffix. */
List <int> longestProperPrefixLengths = LLPPS.Build(pattern);
var indexes = new List <int>();
int i = 0; /* Index to navigate over text */
int j = 0; /* Index to navigate over pattern*/
while (i < text.Length)
{
if (text[i] == pattern[j]) /* When there is a match*/
{
i++; /* Continue incrementing i and j as long as characters match. */
j++;
if (j == pattern.Length) /* Means pattern is matched with text [i-pattern.Length, i-1]*/
{
indexes.Add(i - pattern.Length);
/* Since we are after all occurrences of pattern, continue by changing j (in naive approach after each match, this would be set to zero. )*/
j = longestProperPrefixLengths[j - 1]; /* Label (A) */
}
}
else /* When there is a mismatch, stop and go backward in pattern. Note: always going forward in the text (main string) */
{
if (j == 0) /* means we have navigated backward so much that j is reset to zero at this stage [reset to naive approach], and a one-to-one sequential search of pattern in text, starting at index i, starts again. */
{
i++;
}
else
{
j = longestProperPrefixLengths[j - 1]; /* Label (B) == Label (A) */
}
}
}
return(indexes);
}
