Since nop asked for a fast solution there can be only one arbiter: Benchmark.

I benchmarked the non-golf solutions. The results show that tye's solution is the fastest by quite a margin. 

Test input is 'XYZZY'                             

Benchmark: timing 1000000 iterations                     
     japhy: 28 secs (28.21 usr +  0.01 sys = 28.22 CPU) @ 35435.86/s)
    japhy2: 23 secs (23.57 usr +  0.00 sys = 23.57 CPU) @ 42426.81/s)
    japhy3: 22 secs (21.87 usr +  0.01 sys = 21.88 CPU) @ 45703.84/s)
       jmn:  8 secs ( 7.26 usr +  0.01 sys =  7.27 CPU) @ 137551.58/s)
    merlyn: 20 secs (20.54 usr + -0.02 sys = 20.52 CPU) @ 48732.94/s)
    petral: 22 secs (22.47 usr +  0.01 sys = 22.48 CPU) @ 44483.99/s)
       tye:  5 secs ( 4.84 usr +  0.00 sys =  4.84 CPU) @ 206611.57/s)
           Rate  japhy japhy2 petral japhy3 merlyn    jmn    tye
japhy   35436/s     --   -16%   -20%   -22%   -27%   -74%   -83%
japhy2  42427/s    20%     --    -5%    -7%   -13%   -69%   -79%
petral  44484/s    26%     5%     --    -3%    -9%   -68%   -78%
japhy3  45704/s    29%     8%     3%     --    -6%   -67%   -78%
merlyn  48733/s    38%    15%    10%     7%     --   -65%   -76%
jmn    137552/s   288%   224%   209%   201%   182%     --   -33%
tye    206612/s   483%   387%   364%   352%   324%    50%     --

Test input is 'XYZZZ'

Benchmark: timing 1000000 iterations
     japhy: 28 secs (28.30 usr +  0.00 sys = 28.30 CPU) @ 35335.69/s)
    japhy2: 22 secs (22.45 usr +  0.02 sys = 22.47 CPU) @ 44503.78/s)
    japhy3: 22 secs (21.97 usr +  0.01 sys = 21.98 CPU) @ 45495.91/s)
       jmn: 27 secs (25.95 usr +  0.00 sys = 25.95 CPU) @ 38535.65/s)
    merlyn: 18 secs (18.30 usr +  0.00 sys = 18.30 CPU) @ 54644.81/s)
    petral: 18 secs (18.69 usr +  0.01 sys = 18.70 CPU) @ 53475.94/s)
       tye:  5 secs ( 4.85 usr +  0.00 sys =  4.85 CPU) @ 206185.57/s)
           Rate  japhy    jmn japhy2 japhy3 petral merlyn    tye     
japhy   35336/s     --    -8%   -21%   -22%   -34%   -35%   -83%     
jmn     38536/s     9%     --   -13%   -15%   -28%   -29%   -81%     
japhy2  44504/s    26%    15%     --    -2%   -17%   -19%   -78%     
japhy3  45496/s    29%    18%     2%     --   -15%   -17%   -78%     
petral  53476/s    51%    39%    20%    18%     --    -2%   -74%     
merlyn  54645/s    55%    42%    23%    20%     2%     --   -73%     
tye    206186/s   484%   435%   363%   353%   286%   277%     --

[download]
Update: Added japhy's other solutions. The benchmark code is on my scratchpad.

Update 2: Added petral's solution.

As a general observation. 97% of the Base36 range can be handled with a simple substitution of the last character in the string. This is the test case represented by 'XYZZY' above. The remaining numbers in the Base36 range (those ending in Z) require more work. This is the test case represented by 'XYZZZ'.

All of the above solutions could be optimised for the substitution case. The Z increment is therefore the governing case in determining the speed of the solution.

What's nice about tye's solution is that it takes these factors into account. He wrote it to be fast and it was.


John.

In reply to Re: Base36 numbers: speed and golf by jmcnamara
in thread Base36 numbers: speed and golf by nop

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.