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# rdrewd/problem14_nocache.py Created Nov 26, 2013

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Un-cached implementation of Project Euler problem 14. Fails to meet the "under a minute" time requirement.
 #! `env python` -t def seq(n): """ Generate the sequence for Project Euler problem 14. =================================================== n is a positive integer that is the first number in the sequence. I'm told that although it hasn't been proven, that it is believed that regardless of the starting number, the sequence eventually gets to 1, which is where we stop. 1 2 3 4 5 6 7 8 123456789012345678901234567989012345678901234567890123456789012345678901234567890 """ while True: if n % 2 == 0: next=n/2 else: next=3*n+1 yield n if n == 1: return n=next # end seq def runlen(n): """ runlen returns the length of the sequence generated by seq(n) """ count=0 for s in seq(n): count += 1 # end "for s" return count #end runlen def main(): longest=0 basis=0 for i in xrange(1, 1000000): r=runlen(i) if r > longest: basis=i longest=r # print 'runlen(', i,')=', runlen(i) # end "for i" print "longest=", longest,\ "generated from", basis return basis # end main