[Mono-bugs] [Bug 328036] [PATCH]Casting bug with generic collections

bugzilla_noreply at novell.com bugzilla_noreply at novell.com
Tue Sep 25 20:00:22 EDT 2007


--- Comment #9 from Robert Jordan <robertj at gmx.net>  2007-09-25 18:00:21 MST ---
[Unrelated to the bug]

Assuming that IDictionary.Contains() is actually an O(1) operation, you could
implement Equals more efficiently w/out sorting by simply probing if a key
from d1 is in d2 and if their values are equal. It would be an O (n) operation,
whereas your algorithm is O (n log n).

If you're uncertain whether Contains() is actually an O(1), you can
use a third (true O(1)) dictionary:

Hashtable t = new Hashtable ();

foreach (DictionaryEntry e in d1) {
    t[e.Key] = e.Value;

foreach (DictionaryEntry e in d2) {
    if (!t.Contains (e.Key))
        return false;

    value = t[e.Key];
    if (value != e.Value)
        return false;

This is also an O (n) operation.

For corner cases like "null" keys, you'd need special handling,
because Hashtable doesn't support it.

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