private void Diff(DiffDocument r, DiffDocument c, int i, int j)
{
if (i > 0 && j > 0 && r[i] == c[j]) {
Diff(r, c, i - 1, j - 1);
} else {
if (j > 0 && (i == 0 || table[i][j - 1] >= table[i - 1][j])) {
Diff(r, c, i, j - 1);
if (lastChange == null || lastChange.Type != ChangeType.Add) {
if (lastChange != null) {
changeList.Add(lastChange);
}
lastChange = new Change() { Type = ChangeType.Add, StartPosition1 = i, StartPosition2 = j };
}
lastChange.TextAdded += c[j] + Environment.NewLine;
} else if (i > 0 && (j == 0 || table[i][j - 1] < table[i - 1][j])) {
Diff(r, c, i - 1, j);
if (lastChange == null || lastChange.Type != ChangeType.Remove) {
if (lastChange != null) {
changeList.Add(lastChange);
}
lastChange = new Change() { Type = ChangeType.Remove, StartPosition1 = i, StartPosition2 = j };
}
lastChange.TextDeleted += r[i] + Environment.NewLine;
}
if (lastChange != null) {
lastChange.EndPosition1 = i;
lastChange.EndPosition2 = j;
}
}
}
public DiffDocument Substring(int start, int end)
{
DiffDocument ret = new DiffDocument();
ret.Lines = new string[end - start];
for (int i = start; i < end; i++) {
ret.Lines[i] = Lines[i];
}
return ret;
}
public List<Change> Diff(DiffDocument d1, DiffDocument d2)
{
table = new string[d1.Length][];
for (int i = 0; i < d1.Length; i++) {
table[i] = new string[d2.Length];
}
FindLcs(d1, d2);
Diff(d1, d2, d1.Length - 1, d2.Length - 1);
if (lastChange != null) {
changeList.Add(lastChange);
}
table = null;
return changeList;
}
/// <summary>
/// Find the longest common subsequence of lines across two documents.
/// </summary>
/// <param name="d1">The original document.</param>
/// <param name="d2">The new document.</param>
/// <returns>A string containing the longest common subsequence of identical lines across two documents</returns>
private int FindLcs(DiffDocument d1, DiffDocument d2)
{
if (d2.Length <= 1 || d1.Length <= 1) return 0;
if (table[d1.Length - 1][d2.Length - 1] != -1) {
return table[d1.Length - 1][d2.Length - 1];
}
int lcs;
if (d1[d1.Length - 1] == (d2[d2.Length - 1])) {
// Suppose that two sequences both end in the same element. To find their LCS, shorten each sequence by removing the last element,
// find the LCS of the shortened sequences, and to that LCS append the removed element.
lcs = FindLcs(d1.Substring(0, d1.Length - 2), d2.Substring(0, d2.Length - 2)) + 1;
} else {
// Suppose that the two sequences X and Y do not end in the same symbol. Then the LCS of X and Y is the longest sequence of LCS(Xn,Ym-1) and LCS(Xn-1,Ym).
lcs = Math.Max(FindLcs(d1, d2.Substring(0, d2.Length - 2)), FindLcs(d1.Substring(0, d1.Length - 2), d2));
}
table[d1.Length - 1][d2.Length - 1] = lcs;
return lcs;
}
static void Main(string[] args)
{
string s1 = @"
This part of the
document has stayed the
same from version to
version. It shouldn't
be shown if it doesn't
change. Otherwise, that
would not be helping to
compress the size of the
changes.
This paragraph contains
text that is outdated.
It will be deleted in the
near future.
It is important to spell
check this dokument. On
the other hand, a
misspelled word isn't
the end of the world.
Nothing in the rest of
this paragraph needs to
be changed. Things can
be added after it.";
string s2 = @"
This is an important
notice! It should
therefore be located at
the beginning of this
document!
This part of the
document has stayed the
same from version to
version. It shouldn't
be shown if it doesn't
change. Otherwise, that
would not be helping to
compress anything.
It is important to spell
check this document. On
the other hand, a
misspelled word isn't
the end of the world.
Nothing in the rest of
this paragraph needs to
be changed. Things can
be added after it.
This paragraph contains
important new additions
to this document.";
string[] a = new string[] {@"
a
b
d
e"
};
string[] b = new string[] {@"
a
f
c
d"
};
string[] resultAb = new string[] { @"2a3
> c" };
string[] resultBa = new string[] { @"3d2
< c" };
DiffDocument d1 = new DiffDocument(a[0]);
DiffDocument d2 = new DiffDocument(b[0]);
Console.WriteLine("new Lcs().PrintDiff(d1, d2);");
foreach (Change c in new Lcs().Diff(d1, d2)) {
Console.WriteLine(c);
}
Console.WriteLine("new Lcs().PrintDiff(d2, d1);");
foreach (Change c in new Lcs().Diff(d2, d1)) {
Console.WriteLine(c);
}
Console.ReadKey();
}