public static bool IsPermutation <T>(
this ArrayIterator <T> first1,
ArrayIterator <T> last1,
ArrayIterator <T> first2,
Func <T, T, bool> pred
)
{
first1.Mismatch(last1, first2, pred, out first1, out first2);
if (first1.IsEqual(last1))
{
return(true);
}
var last2 = first2;
last2 = last2.GetAdvanced(first1.Distance(last1));
for (var it1 = first1; it1.NotEqual(last1); it1 = it1.GetNext())
{
if (first1.Find(it1, it1.GetCurrent(), pred).IsEqual(it1))
{
var n = first2.Count(last2, it1.GetCurrent(), pred);
if (n == 0 || it1.Count(last1, it1.GetCurrent(), pred) != n)
{
return(false);
}
}
}
return(true);
}