protected override string DoCompare <T>(IList <T> src, IList <T> dst, Comparison <T> comp)
{
var sn = src.Count;
var dn = dst.Count;
while (sn > 0 && dn > 0 && comp(src[sn - 1], dst[dn - 1]) == 0)
{
--sn;
--dn;
}
if (sn == 0)
{
return(new StringBuilder(dst.Count).Append('A', dn).Append('C', src.Count).ToString());
}
if (dn == 0)
{
return(new StringBuilder(src.Count).Append('D', sn).Append('C', dst.Count).ToString());
}
var heads = new Head[sn + dn + 3];
var z = heads.Length - 2;
var orig = sn + 1;
var goal = dn + 1;
heads[orig].Tra = null;
for (var i = 1; i < z; i++)
{
var min = orig - i + 1;
var max = orig + i - 1;
for (var p = min; p <= max; p += 2)
{
if (p < 1 || p > z)
{
continue;
}
var s = heads[p].Src;
var d = heads[p].Dst;
var r = heads[p].Tra;
// Find a snake.
var u = 0;
while (s + u < sn && d + u < dn && comp(src[s + u], dst[d + u]) == 0)
{
u++;
}
if (u > 0)
{
s += u;
d += u;
r += Trace.C(u);
}
// Recognize a difference.
if (heads[p - 1].Src + heads[p - 1].Dst <= s + d)
{
heads[p - 1].Src = s + 1;
heads[p - 1].Dst = d;
heads[p - 1].Tra = r + Trace.D;
}
if (heads[p + 1].Src + heads[p + 1].Dst <= s + d)
{
heads[p + 1].Src = s;
heads[p + 1].Dst = d + 1;
heads[p + 1].Tra = r + Trace.A;
}
}
// See if we have reached the goal.
if (heads[goal].Src >= sn && heads[goal].Dst >= dn)
{
int posts = src.Count - sn;
return(heads[goal].Tra.ToStringBuilder(posts).Append('C', posts).ToString());
}
}
throw new ApplicationException("Edit matrix overrun. It means this program has a bug in it.");
}