Hello! I have solved problem 89 using analytic way, i.e, the length of the string will always be constant, so repeated substitutions and differentiating will make way(i got answer as "c"). But is there any method by using logic that will provide a solution even faster, and is there any technique? Also i am a noob, so can you suggest me a good book (available on the internet free) which goes through these concepts in more detalil?
closed as unclear what you're asking by John Rennie, Chris♦, Kyle Kanos, heather, FGSUZ Apr 19 at 11:07
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