Geoframer wrote: > Hi everyone, > > The problem is to compute the number of trailing zero's in factorials > (n! = 1*2*3*4*.......*n). with n <= 1000000000 > > My solution is as follows (a = times to read a number (b) to process) : > > --------------------------------------------------------------------------- > > a = input() > for i in range(a): > lst = (5, 25, 125, 625, 3125, 15625, 78125, 390625, 1953125, > 9765625, 48828125, 244140625) > ans = 0 > b = input() > for i in lst: > if i <= b: > ans += b//i > print ans > > ---------------------------------------------------------------------------- > > Please, if you have suggestions to improve the speed of this algorithm > give an argumentation as to why a certain something is faster. > That would allow me to learn to program faster algorithms in Python al > together instead of just in this problem.
Try putting the actual computation into a function. Make any variable that is used more than once a local variable of the function (ans, b,i). Accessing local variables is faster than accessing global variables. This gives about 40% speedup in my tests. Use psyco if it is available in your contest, for me that shaved off another 30-50%; you will get more benefit from psyco the more iterations you have, because psyco introduces some compilation overhead that has to be made up by the faster code. http://psyco.sourceforge.net/ You really aren't doing much so there's not a lot to optimize that I can see. You could try asking on comp.lang.python, lots of people there are good at optimization. Kent _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
