static List <EditDistanceMatchObject> DeleteN(string s, int index, int n)
{
List <EditDistanceMatchObject> toReturn = new List <EditDistanceMatchObject>();
EditDistanceMatchObject rowAsEDMO = new EditDistanceMatchObject
{
Index = index,
DeletedIndices = new List <int>(),
Substring = s
};
toReturn.Add(rowAsEDMO);
List <EditDistanceMatchObject> currentGeneration = toReturn;
for (int i = 0; i < n; i++)
{
List <EditDistanceMatchObject> nextGeneration = new List <EditDistanceMatchObject>();
foreach (var element in currentGeneration)
{
nextGeneration.AddRange(DeleteOneMore(element));
}
toReturn.AddRange(nextGeneration);
currentGeneration = nextGeneration;
}
return(toReturn);
}
/// <summary>
/// Assumes substrings match
/// </summary>
/// <returns></returns>
static int EditDistance(EditDistanceMatchObject e1, EditDistanceMatchObject e2)
{
int toReturn = 0;
//We will verify that the union of deleted indices has size at most n
//Indices to deleted indices. It is also the index offset to the diff string. I know that doesn't make sense, but it's meant to be a clue as to why the algorithm works.
int i1 = 0, i2 = 0;
while (i1 < e1.DeletedIndices.Count && i2 < e2.DeletedIndices.Count)
{
int nextString1Index = e1.DeletedIndices[i1] + i2;
int nextString2Index = e2.DeletedIndices[i2] + i1;
if (nextString1Index < nextString2Index)
{
i1++;
}
else if (nextString2Index < nextString1Index)
{
i2++;
}
else
{
i1++;
i2++;
}
toReturn++;
}
toReturn += e1.DeletedIndices.Count - i1 + e2.DeletedIndices.Count - i2;
return(toReturn);
}
static List <EditDistanceMatchObject> DeleteOneMore(EditDistanceMatchObject edmo)
{
List <EditDistanceMatchObject> toReturn = new List <EditDistanceMatchObject>();
int oldStringLength = edmo.Substring.Length;
int oldDeletedIndexCount = edmo.DeletedIndices.Count;
int minDeletionIndex = oldDeletedIndexCount == 0 ? 0 : edmo.DeletedIndices.Max() + 1;
int maxDeletionIndex = oldStringLength + oldDeletedIndexCount - 1;
for (int i = minDeletionIndex; i <= maxDeletionIndex; i++)
{
EditDistanceMatchObject toAdd = new EditDistanceMatchObject
{
DeletedIndices = edmo.DeletedIndices.Select(index => index).ToList(),
Index = edmo.Index,
Substring = edmo.Substring.Remove(i - oldDeletedIndexCount, 1)
};
toAdd.DeletedIndices.Add(i);
toReturn.Add(toAdd);
}
return(toReturn);
}
