public static int Difference <T>(T[] a, T[] b)
{
EfficientArray <T> a1 = new EfficientArray <T>(a);
EfficientArray <T> b1 = new EfficientArray <T>(b);
return(Difference(a1, b1));
}
public static int Difference <T>(EfficientArray <T> a, EfficientArray <T> b)
{
if (a.Length == 0)
{
return(b.Length);
}
if (b.Length == 0)
{
return(a.Length);
}
int[,] lcs = PositionAndLengthLcs(a, b);
if (lcs[0, 1] == 0)
{//no substrings
return(Math.Max(a.Length, b.Length));
}
EfficientArray <T> a1 = SubArray(a, 0, lcs[0, 0]);
EfficientArray <T> b1 = SubArray(b, 0, lcs[1, 0]);
int upperA = lcs[0, 0] + lcs[0, 1], upperB = lcs[1, 0] + lcs[1, 1];
EfficientArray <T> a2 = SubArray(a, upperA, a.Length - upperA);
EfficientArray <T> b2 = SubArray(b, upperB, b.Length - upperB);
return(Difference(a1, b1) + Difference(a2, b2));
}
public static int[,] PositionAndLengthLcs <T>(EfficientArray <T> a, EfficientArray <T> b)
{
var lengths = new int[a.Length, b.Length];
int greatestLength = 0;
int[,] positionAndLengthLcs = new int[2, 2]; //position and length, for a and b
for (int i = 0; i < a.Length; i++)
{
for (int j = 0; j < b.Length; j++)
{
if (a[i].Equals(b[j]))
{
lengths[i, j] = i == 0 || j == 0 ? 1 : lengths[i - 1, j - 1] + 1;
if (lengths[i, j] > greatestLength)
{
greatestLength = lengths[i, j];
positionAndLengthLcs[0, 0] = i - greatestLength + 1;
positionAndLengthLcs[0, 1] = greatestLength;
positionAndLengthLcs[1, 0] = j - greatestLength + 1;
positionAndLengthLcs[1, 1] = greatestLength;
}
}
else
{
lengths[i, j] = 0;
}
}
}
return(positionAndLengthLcs);
}
public static EfficientArray <T> SubArray <T>(this EfficientArray <T> data, int index, int length)
{
return(new EfficientArray <T>(data, index, length));
}
public EfficientArray(EfficientArray <T> array, int startIndex, int length)
{
this.array = array.array;
this.startIndex = startIndex;
this.length = length;
}
public EfficientArray(EfficientArray <T> array)
{
this.array = array.array;
startIndex = array.startIndex;
length = array.length;
}
