compare a list of integers

[Tem]

List<inta = new List<int>();
a.Add(1);
a.Add(2);
a.Add(3);

List<intb = new List<int>();
b.Add(1);
b.Add(2);
b.Add(3);

I need to compare two integer lists.
It returns true if values and ordering are the same.
Is there a better way to do this than a foreach loop?

Tem

[Jon Skeet [C# MVP]]

Re: compare a list of integers

Tem <tem1232@yahoo. comwrote:

List<inta = new List<int>();
a.Add(1);
a.Add(2);
a.Add(3);
>
List<intb = new List<int>();
b.Add(1);
b.Add(2);
b.Add(3);
>
I need to compare two integer lists.
It returns true if values and ordering are the same.
Is there a better way to do this than a foreach loop?

Which version of .NET are you using? .NET 3.5 has an extension method
on IEnumerable<Tof SequenceEqual:

if (a.SequenceEqua l(b))
....

--
Jon Skeet - <skeet@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
World class .NET training in the UK: http://iterativetraining.co.uk

[Tem]

Re: compare a list of integers

3.5
but I thought extension methods would make things slow? been trying to avoid
them


"Jon Skeet [C# MVP]" <skeet@pobox.co mwrote in message
news:MPG.227e4f bd1f62c6a5c8d@m snews.microsoft .com...

Tem <tem1232@yahoo. comwrote:

>List<inta = new List<int>();
>a.Add(1);
>a.Add(2);
>a.Add(3);
>>
>List<intb = new List<int>();
>b.Add(1);
>b.Add(2);
>b.Add(3);
>>
>I need to compare two integer lists.
>It returns true if values and ordering are the same.
>Is there a better way to do this than a foreach loop?

>
Which version of .NET are you using? .NET 3.5 has an extension method
on IEnumerable<Tof SequenceEqual:
>
if (a.SequenceEqua l(b))
...
>
--
Jon Skeet - <skeet@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
World class .NET training in the UK: http://iterativetraining.co.uk

[Marc Gravell]

Re: compare a list of integers

but I thought extension methods would make things slow? been trying to avoid

them

Why would you think that? OK, in reality you could shave a few cycles
if you know you have List<Tby checking the length first
(SequenceEqual doesn't do this, although this could be a missed
opportunity - it could check if both operands implement IList, and
compare the length) - and because it is using the interface (rather
than direct to the sealed List<T>) it won't inline any of the fetches
- but this is rarely the most significant thing.

My advice: use the simplest code that clearly expresses what you want
to do. SequenceEqual does this; *if* you later find this is a
bottleneck, then tweak it (perhaps introduce a List<TSequenceE qual
extension method) - but until then you're optimising prematurely.

Marc

[Marc Gravell]

Re: compare a list of integers

For reference - an additional overload that checks a few obvious cases
first... just add your namespace as a "using" at the top, and the
overload resolution will select it instead of
Enumerable.Sequ enceEqual, since ICollection<Tis more specific than
IEnumerable<T>

Adding a List<T>-specific version would almost certainly be overkill;
I doubt you'd ever see any tangible performance benefit in most code.

Marc

namespace SomeNamespace
{
public static class CollectionExt
{
public static bool SequenceEqual<T >(this ICollection<Tfi rst,
ICollection<Tse cond)
{
return SequenceEqual<T >(first, second,
EqualityCompare r<T>.Default);
}
public static bool SequenceEqual<T >(this ICollection<Tfi rst,
ICollection<Tse cond, IEqualityCompar er<Tcomparer)
{
if (first == null) throw new
ArgumentNullExc eption("first") ;
if (second == null) throw new
ArgumentNullExc eption("second" );
if (ReferenceEqual s(first, second)) return true;
if (first.Count != second.Count) return false;
return System.Linq.Enu merable.Sequenc eEqual<T>(first ,
second, comparer);
}
}
}

[Tem]

Re: compare a list of integers

Thanks Marc

Something tells me this will be much more efficient.

"Marc Gravell" <marc.gravell@g mail.comwrote in message
news:98ec5ecf-e8cc-48fc-9429-aeb8e7a580ad@24 g2000hsh.google groups.com...

For reference - an additional overload that checks a few obvious cases
first... just add your namespace as a "using" at the top, and the
overload resolution will select it instead of
Enumerable.Sequ enceEqual, since ICollection<Tis more specific than
IEnumerable<T>
>
Adding a List<T>-specific version would almost certainly be overkill;
I doubt you'd ever see any tangible performance benefit in most code.
>
Marc
>
namespace SomeNamespace
{
public static class CollectionExt
{
public static bool SequenceEqual<T >(this ICollection<Tfi rst,
ICollection<Tse cond)
{
return SequenceEqual<T >(first, second,
EqualityCompare r<T>.Default);
}
public static bool SequenceEqual<T >(this ICollection<Tfi rst,
ICollection<Tse cond, IEqualityCompar er<Tcomparer)
{
if (first == null) throw new
ArgumentNullExc eption("first") ;
if (second == null) throw new
ArgumentNullExc eption("second" );
if (ReferenceEqual s(first, second)) return true;
if (first.Count != second.Count) return false;
return System.Linq.Enu merable.Sequenc eEqual<T>(first ,
second, comparer);
}
}
}

[Jon Skeet [C# MVP]]

Re: compare a list of integers

Tem <tem1232@yahoo. comwrote:

Something tells me this will be much more efficient.

Certainly in the special cases, where the two lists are either
"obviously" different or "obviously" the same.

But note that it's still an extension method - your earlier comment
about how you've been "trying to avoid [extension methods]" should be
reconsidered, IMO.

--
Jon Skeet - <skeet@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
World class .NET training in the UK: http://iterativetraining.co.uk