/// <summary>
/// In the edit graph for the sequences src and des, search for the
/// optimal(shortest) path from (src.StartIndex, des.StartIndex) to
/// (src.EndIndex, des.EndIndex).
///
/// The searching starts from both ends of the graph and when the
/// furthest forward reaching overlaps with the furthest backward
/// reaching, the overlapped point is reported as the middle point
/// of the shortest path.
///
/// See the listed reference for the detailed description of the
/// algorithm
/// </summary>
/// <param name="src">
/// Represents a (sub)sequence of _original
/// </param>
/// <param name="des">
/// Represents a (sub)sequence of _modified
/// </param>
/// <returns>
/// The found middle snake
/// </returns>
private MiddleSnake findMiddleSnake(Sequence src, Sequence des)
{
int d, k;
int x, y;
MiddleSnake midSnake = new MiddleSnake();
// the range of diagonal values
int minDiag = src.StartIndex - des.EndIndex;
int maxDiag = src.EndIndex - des.StartIndex;
// middle point of forward searching
int fwdMid = src.StartIndex - des.StartIndex;
// middle point of backward searching
int bwdMid = src.EndIndex - des.EndIndex;
// forward seaching range
int fwdMin = fwdMid;
int fwdMax = fwdMid;
// backward seaching range
int bwdMin = bwdMid;
int bwdMax = bwdMid;
bool odd = ((fwdMin - bwdMid) & 1) == 1;
fwdVector[fwdMid] = src.StartIndex;
bwdVector[bwdMid] = src.EndIndex;
#if (MyDEBUG)
Debug.WriteLine("-- Entering Function findMiddleSnake(src, des) --");
#endif
for (d = 1; ; d++)
{
// extend or shrink the search range
if (fwdMin > minDiag)
{
fwdVector[--fwdMin - 1] = -1;
}
else
{
++fwdMin;
}
if (fwdMax < maxDiag)
{
fwdVector[++fwdMax + 1] = -1;
}
else
{
--fwdMax;
}
#if (MyDEBUG)
Debug.WriteLine(d, " D path");
#endif
// top-down search
for (k = fwdMax; k >= fwdMin; k -= 2)
{
if (fwdVector[k - 1] < fwdVector[k + 1])
{
x = fwdVector[k + 1];
}
else
{
x = fwdVector[k - 1] + 1;
}
y = x - k;
midSnake.Source.StartIndex = x;
midSnake.Destination.StartIndex = y;
while (x < src.EndIndex &&
y < des.EndIndex &&
_original[x].CompareTo(_modified[y]) == 0)
{
x++;
y++;
}
// update forward vector
fwdVector[k] = x;
#if (MyDEBUG)
Debug.WriteLine(" Inside forward loop");
Debug.WriteLine(k, " Diagonal value");
Debug.WriteLine(x, " X value");
Debug.WriteLine(y, " Y value");
#endif
if (odd && k >= bwdMin && k <= bwdMax && x >= bwdVector[k])
{
// this is the snake we are looking for
// and set the end indeses of the snake
midSnake.Source.EndIndex = x;
midSnake.Destination.EndIndex = y;
midSnake.SES_Length = 2 * d - 1;
#if (MyDEBUG)
Debug.WriteLine("!!!Report snake from forward search");
Debug.WriteLine(midSnake.Source.StartIndex, " middle snake source start index");
Debug.WriteLine(midSnake.Source.EndIndex, " middle snake source end index");
Debug.WriteLine(midSnake.Destination.StartIndex, " middle snake destination start index");
Debug.WriteLine(midSnake.Destination.EndIndex, " middle snake destination end index");
#endif
return(midSnake);
}
}
// extend the search range
if (bwdMin > minDiag)
{
bwdVector[--bwdMin - 1] = int.MaxValue;
}
else
{
++bwdMin;
}
if (bwdMax < (maxDiag - 1))
{
bwdVector[++bwdMax + 1] = int.MaxValue;
}
else
{
--bwdMax;
}
// bottom-up search
for (k = bwdMax; k >= bwdMin; k -= 2)
{
if (bwdVector[k - 1] < bwdVector[k + 1])
{
x = bwdVector[k - 1];
}
else
{
x = bwdVector[k + 1] - 1;
}
y = x - k;
midSnake.Source.EndIndex = x;
midSnake.Destination.EndIndex = y;
while (x > src.StartIndex &&
y > des.StartIndex &&
_original[x - 1].CompareTo(_modified[y - 1]) == 0)
{
x--;
y--;
}
// update backward Vector
bwdVector[k] = x;
#if (MyDEBUG)
Debug.WriteLine(" Inside backward loop");
Debug.WriteLine(k, " Diagonal value");
Debug.WriteLine(x, " X value");
Debug.WriteLine(y, " Y value");
#endif
if (!odd && k >= fwdMin && k <= fwdMax && x <= fwdVector[k])
{
// this is the snake we are looking for
// and set the start indexes of the snake
midSnake.Source.StartIndex = x;
midSnake.Destination.StartIndex = y;
midSnake.SES_Length = 2 * d;
#if (MyDEBUG)
Debug.WriteLine("!!!Report snake from backward search");
Debug.WriteLine(midSnake.Source.StartIndex, " middle snake source start index");
Debug.WriteLine(midSnake.Source.EndIndex, " middle snake source end index");
Debug.WriteLine(midSnake.Destination.StartIndex, " middle snake destination start index");
Debug.WriteLine(midSnake.Destination.EndIndex, " middle snake destination end index");
#endif
return(midSnake);
}
}
}
}
/// <summary>
/// In the edit graph for the sequences src and des, search for the
/// optimal(shortest) path from (src.StartIndex, des.StartIndex) to
/// (src.EndIndex, des.EndIndex).
///
/// The searching starts from both ends of the graph and when the
/// furthest forward reaching overlaps with the furthest backward
/// reaching, the overlapped point is reported as the middle point
/// of the shortest path.
///
/// See the listed reference for the detailed description of the
/// algorithm
/// </summary>
/// <param name="src">
/// Represents a (sub)sequence of _original
/// </param>
/// <param name="desc">
/// Represents a (sub)sequence of _modified
/// </param>
/// <returns>
/// The found middle snake
/// </returns>
private MiddleSnake findMiddleSnake(Sequence src, Sequence des)
{
int d, k;
int x, y;
MiddleSnake midSnake = new MiddleSnake();
// the range of diagonal values
int minDiag = src.StartIndex - des.EndIndex;
int maxDiag = src.EndIndex - des.StartIndex;
// middle point of forward searching
int fwdMid = src.StartIndex - des.StartIndex;
// middle point of backward searching
int bwdMid = src.EndIndex - des.EndIndex;
// forward seaching range
int fwdMin = fwdMid;
int fwdMax = fwdMid;
// backward seaching range
int bwdMin = bwdMid;
int bwdMax = bwdMid;
bool odd = ((fwdMin - bwdMid) & 1) == 1;
fwdVector[fwdMid] = src.StartIndex;
bwdVector[bwdMid] = src.EndIndex;
#if (MyDEBUG)
Debug.WriteLine("-- Entering Function findMiddleSnake(src, des) --");
#endif
for (d = 1; ; d++)
{
// extend or shrink the search range
if (fwdMin > minDiag)
fwdVector[--fwdMin -1] = -1;
else
++fwdMin;
if(fwdMax < maxDiag)
fwdVector[++fwdMax +1] = -1;
else
--fwdMax;
#if (MyDEBUG)
Debug.WriteLine(d, " D path");
#endif
// top-down search
for (k = fwdMax; k >= fwdMin; k -= 2)
{
if (fwdVector[k-1] < fwdVector[k+1])
{
x = fwdVector[k+1];
}
else
{
x = fwdVector[k-1] + 1;
}
y = x - k;
midSnake.Source.StartIndex = x;
midSnake.Destination.StartIndex = y;
while (x < src.EndIndex &&
y < des.EndIndex &&
_original[x].CompareTo(_modified[y]) == 0)
{
x++;
y++;
}
// update forward vector
fwdVector[k] = x;
#if (MyDEBUG)
Debug.WriteLine(" Inside forward loop");
Debug.WriteLine(k, " Diagonal value");
Debug.WriteLine(x, " X value");
Debug.WriteLine(y, " Y value");
#endif
if (odd && k >= bwdMin && k <= bwdMax && x >= bwdVector[k])
{
// this is the snake we are looking for
// and set the end indeses of the snake
midSnake.Source.EndIndex = x;
midSnake.Destination.EndIndex = y;
midSnake.SES_Length = 2 * d -1;
#if (MyDEBUG)
Debug.WriteLine("!!!Report snake from forward search");
Debug.WriteLine(midSnake.Source.StartIndex, " middle snake source start index");
Debug.WriteLine(midSnake.Source.EndIndex, " middle snake source end index");
Debug.WriteLine(midSnake.Destination.StartIndex, " middle snake destination start index");
Debug.WriteLine(midSnake.Destination.EndIndex, " middle snake destination end index");
#endif
return midSnake;
}
}
// extend the search range
if (bwdMin > minDiag)
bwdVector[--bwdMin -1] = int.MaxValue;
else
++bwdMin;
if(bwdMax < (maxDiag - 1))
bwdVector[++bwdMax +1] = int.MaxValue;
else
--bwdMax;
// bottom-up search
for (k = bwdMax; k >= bwdMin; k -= 2)
{
if (bwdVector[k - 1] < bwdVector[k + 1])
{
x = bwdVector[k - 1];
}
else
{
x = bwdVector[k + 1] - 1;
}
y = x - k;
midSnake.Source.EndIndex = x;
midSnake.Destination.EndIndex = y;
while (x > src.StartIndex &&
y > des.StartIndex &&
_original[x-1].CompareTo(_modified[y-1]) == 0)
{
x--;
y--;
}
// update backward Vector
bwdVector[k] = x;
#if (MyDEBUG)
Debug.WriteLine(" Inside backward loop");
Debug.WriteLine(k, " Diagonal value");
Debug.WriteLine(x, " X value");
Debug.WriteLine(y, " Y value");
#endif
if (!odd && k >= fwdMin && k <= fwdMax && x <= fwdVector[k])
{
// this is the snake we are looking for
// and set the start indexes of the snake
midSnake.Source.StartIndex = x;
midSnake.Destination.StartIndex = y;
midSnake.SES_Length = 2 * d;
#if (MyDEBUG)
Debug.WriteLine("!!!Report snake from backward search");
Debug.WriteLine(midSnake.Source.StartIndex, " middle snake source start index");
Debug.WriteLine(midSnake.Source.EndIndex, " middle snake source end index");
Debug.WriteLine(midSnake.Destination.StartIndex, " middle snake destination start index");
Debug.WriteLine(midSnake.Destination.EndIndex, " middle snake destination end index");
#endif
return midSnake;
}
}
}
}