private static void BuildModificationData(ModificationData A, int startA, int endA, ModificationData B, int startB, int endB, int[] forwardDiagonal, int[] reverseDiagonal)
{
while (startA < endA && startB < endB && A.HashedPieces[startA].Equals(B.HashedPieces[startB]))
{
startA++;
startB++;
}
while (startA < endA && startB < endB && A.HashedPieces[endA - 1].Equals(B.HashedPieces[endB - 1]))
{
endA--;
endB--;
}
int aLength = endA - startA;
int bLength = endB - startB;
if (aLength > 0 && bLength > 0)
{
EditLengthResult res = CalculateEditLength(A.HashedPieces, startA, endA, B.HashedPieces, startB, endB, forwardDiagonal, reverseDiagonal);
if (res.EditLength <= 0)
{
return;
}
if (res.LastEdit == Edit.DeleteRight && res.StartX - 1 > startA)
{
A.Modifications[--res.StartX] = true;
}
else if (res.LastEdit == Edit.InsertDown && res.StartY - 1 > startB)
{
B.Modifications[--res.StartY] = true;
}
else if (res.LastEdit == Edit.DeleteLeft && res.EndX < endA)
{
A.Modifications[res.EndX++] = true;
}
else if (res.LastEdit == Edit.InsertUp && res.EndY < endB)
{
B.Modifications[res.EndY++] = true;
}
BuildModificationData(A, startA, res.StartX, B, startB, res.StartY, forwardDiagonal, reverseDiagonal);
BuildModificationData(A, res.EndX, endA, B, res.EndY, endB, forwardDiagonal, reverseDiagonal);
}
else if (aLength > 0)
{
for (int i = startA; i < endA; i++)
{
A.Modifications[i] = true;
}
}
else if (bLength > 0)
{
for (int i = startB; i < endB; i++)
{
B.Modifications[i] = true;
}
}
}
private static EditLengthResult CalculateEditLength(int[] A, int startA, int endA, int[] B, int startB, int endB, int[] forwardDiagonal, int[] reverseDiagonal)
{
if (null == A)
{
throw new ArgumentNullException("A");
}
if (null == B)
{
throw new ArgumentNullException("B");
}
if (A.Length == 0 && B.Length == 0)
{
return(new EditLengthResult());
}
Edit lastEdit;
int N = endA - startA;
int M = endB - startB;
int MAX = M + N + 1;
int HALF = MAX / 2;
int delta = N - M;
bool deltaEven = delta % 2 == 0;
forwardDiagonal[1 + HALF] = 0;
reverseDiagonal[1 + HALF] = N + 1;
for (int D = 0; D <= HALF; D++)
{
// forward D-path
for (int k = -D; k <= D; k += 2)
{
int kIndex = k + HALF;
int x, y;
if (k == -D || (k != D && forwardDiagonal[kIndex - 1] < forwardDiagonal[kIndex + 1]))
{
x = forwardDiagonal[kIndex + 1]; // y up move down from previous diagonal
lastEdit = Edit.InsertDown;
}
else
{
x = forwardDiagonal[kIndex - 1] + 1; // x up move right from previous diagonal
lastEdit = Edit.DeleteRight;
}
y = x - k;
int startX = x;
int startY = y;
while (x < N && y < M && A[x + startA] == B[y + startB])
{
x += 1;
y += 1;
}
forwardDiagonal[kIndex] = x;
if (!deltaEven)
{
int revX, revY;
if (k - delta >= (-D + 1) && k - delta <= (D - 1))
{
int revKIndex = (k - delta) + HALF;
revX = reverseDiagonal[revKIndex];
revY = revX - k;
if (revX <= x && revY <= y)
{
var res = new EditLengthResult();
res.EditLength = 2 * D - 1;
res.StartX = startX + startA;
res.StartY = startY + startB;
res.EndX = x + startA;
res.EndY = y + startB;
res.LastEdit = lastEdit;
return(res);
}
}
}
}
// reverse D-path
for (int k = -D; k <= D; k += 2)
{
int kIndex = k + HALF;
int x, y;
if (k == -D || (k != D && reverseDiagonal[kIndex + 1] <= reverseDiagonal[kIndex - 1]))
{
x = reverseDiagonal[kIndex + 1] - 1; // move left from k+1 diagonal
lastEdit = Edit.DeleteLeft;
}
else
{
x = reverseDiagonal[kIndex - 1]; //move up from k-1 diagonal
lastEdit = Edit.InsertUp;
}
y = x - (k + delta);
int endX = x;
int endY = y;
while (x > 0 && y > 0 && A[startA + x - 1] == B[startB + y - 1])
{
x -= 1;
y -= 1;
}
reverseDiagonal[kIndex] = x;
if (deltaEven)
{
int forX, forY;
if (k + delta >= -D && k + delta <= D)
{
int forKIndex = (k + delta) + HALF;
forX = forwardDiagonal[forKIndex];
forY = forX - (k + delta);
if (forX >= x && forY >= y)
{
var res = new EditLengthResult();
res.EditLength = 2 * D;
res.StartX = x + startA;
res.StartY = y + startB;
res.EndX = endX + startA;
res.EndY = endY + startB;
res.LastEdit = lastEdit;
return(res);
}
}
}
}
}
throw new Exception("Should never get here");
}