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in reply to Data structure challenge

Trouble is caused by initialisation, so what data structure to use that is initialized in constant time? The answer may be to use simple strings for A and B. The length should be U*log_10(U) so that each group of log_10(U) characters represents an "array element". Initialisation can be done using pack that should be constant time, array access can be simulated using substr which is also constant time.

Just my 2 cents, might be totally wrong, -gjb-

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Re: Data structure challenge
by Abigail-II (Bishop) on Mar 17, 2004 at 20:58 UTC
    Initialisation can be done using pack that should be constant time
    Well, that would be interesting. I'm not a pack() wizard, and I can't see how I would do it with pack. What format would I use?

    Abigail

[reply]

      Wouldn't a pack(a[U*log_10(U)], 'z') do the trick?

      Thanks Aristotle, I was too lazy/huried to check the correct syntax. The length of the string we want to allocate is N = U*ceil(log_10(U)), so I hoped pack(aN, '') would create a string of N '\0' characters using some low level memory allocation function. Unfortunately that doesn't seem to happen, the resulting string consists of N spaces, so there goes constant time... :(

      Just my 2 cents, -gjb-

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        That isn't valid Perl. What exactly were you thinking of?

        I too though that if there's any way to achieve this, pack will be it, but there doesn't seem to be any pack format that would leave any part of the result string uninitialized.

        Makeshifts last the longest.

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