public int LevenshteinDistance <T>(T[] strOld,
T[] strNew,
IEqualityComparer <T> comparer = null,
Func <Choice <T>, int> weight = null,
bool allowTransposition = false)
{
var m1 = strOld.Length + 1;
var m2 = strNew.Length + 1;
if (comparer == null)
{
comparer = EqualityComparer <T> .Default;
}
if (weight == null)
{
weight = c => 1;
}
_ResizeArray(m1, m2);
_num[0, 0] = 0;
for (var i = 1; i < m1; i++)
{
_num[i, 0] = _num[i - 1, 0] + weight(Choice <T> .Remove(strOld[i - 1]));
}
for (var j = 1; j < m2; j++)
{
_num[0, j] = _num[0, j - 1] + weight(Choice <T> .Add(strNew[j - 1]));
}
for (var i = 1; i < m1; i++)
{
for (var j = 1; j < m2; j++)
{
if (comparer.Equals(strOld[i - 1], strNew[j - 1]))
{
_num[i, j] = _num[i - 1, j - 1];
}
else
{
_num[i, j] = Math.Min(Math
.Min(
_num[i - 1, j] + weight(Choice <T> .Remove(strOld[i - 1])),
_num[i, j - 1] + weight(Choice <T> .Add(strNew[j - 1]))
),
_num[i - 1, j - 1] + weight(Choice <T> .Substitute(strOld[i - 1], strNew[j - 1]))
);
if (allowTransposition && i > 1 &&
j > 1 &&
comparer.Equals(strOld[i - 1], strNew[j - 2]) &&
comparer.Equals(strOld[i - 2], strNew[j - 1]))
{
_num[i, j] = Math.Min(_num[i, j],
_num[i - 2, j - 2] + weight(Choice <T> .Transpose(strOld[i - 1], strOld[i - 2])));
}
}
}
}
return(_num[m1 - 1, m2 - 1]);
}
public List <Choice <T> > LevenshteinChoices <T>(T[] strOld,
T[] strNew,
IEqualityComparer <T> comparer = null,
Func <Choice <T>, int> weight = null)
{
if (comparer == null)
{
comparer = EqualityComparer <T> .Default;
}
if (weight == null)
{
weight = c => 1;
}
LevenshteinDistance(strOld, strNew, comparer, weight);
var i = strOld.Length;
var j = strNew.Length;
var result = new List <Choice <T> >();
while (i > 0 && j > 0)
{
if (comparer.Equals(strOld[i - 1], strNew[j - 1]))
{
result.Add(Choice <T> .Equal(strOld[i - 1]));
i = i - 1;
j = j - 1;
}
else
{
var cRemove = Choice <T> .Remove(strOld[i - 1]);
var cAdd = Choice <T> .Add(strNew[j - 1]);
var cSubstitute = Choice <T> .Substitute(strOld[i - 1], strNew[j - 1]);
var remove = _num[i - 1, j] + weight(cRemove);
var add = _num[i, j - 1] + weight(cAdd);
var substitute = _num[i - 1, j - 1] + weight(cSubstitute);
var min = Math.Min(remove, Math.Min(add, substitute));
if (substitute == min)
{
result.Add(cSubstitute);
i = i - 1;
j = j - 1;
}
else if (remove == min)
{
result.Add(cRemove);
i = i - 1;
}
else if (add == min)
{
result.Add(cAdd);
j = j - 1;
}
}
}
while (i > 0)
{
result.Add(Choice <T> .Remove(strOld[i - 1]));
i = i - 1;
}
while (j > 0)
{
result.Add(Choice <T> .Add(strNew[j - 1]));
j = j - 1;
}
result.Reverse();
return(result);
}