>
> <snip>
>
> Your python code as is clocked about 72 seconds on my notebook. The
> following came in at about 4.6 seconds (just has a small trick of reusing
> earlier results)
>
> import time
> start =time.time()
> longest = None
> longest_elements = 0
> solved = {}
> for val in xrange(1,1000000) :
> counter = 1
> number = val
> while number != 1 :
> number = number / 2 if number % 2 == 0 else 3 * number + 1
> if number in solved :
> counter = counter + solved[number]
> break
> else :
> counter = counter + 1
> if counter > longest_elements :
> longest_elements = counter
> longest = val
> solved[val] = counter
> end = time.time()
> print "Time:", end - start
> print longest, ':', longest_elements
>
> Dhananjay
>
>
If you are still looking forward to squeeze around 200ms more, try bit ops -
Original code by Dhananjay averages to 4.25823163986s on my machine
While if you change -
number = number / 2 if number % 2 == 0 else 3 * number + 1
into
number = 3*number+1 if number&1 else number >> 1
it averages 4.058642069496667s on my machine.
Abhishek
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