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Topic: new york times problem solving test (Read 1109 times) |
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rloginunix
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Re: new york times problem solving test
« Reply #1 on: Aug 25th, 2015, 9:45am » |
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The perils of finding a formula for a finite series ... Being a C programmer guess what "the rule" I came up with when is saw 21, 22, 23.
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rmsgrey
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Re: new york times problem solving test
« Reply #2 on: Aug 25th, 2015, 11:25am » |
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The real trick is not so much figuring out a suitable rule, as figuring out ways to test potential rules...
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JiNbOtAk
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Re: new york times problem solving test
« Reply #3 on: Sep 1st, 2015, 6:56pm » |
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So, how many of us intentionally tried getting a "No" ? How many "No"s did you try to get before you were satisfied with the 'rule' ?
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Quis custodiet ipsos custodes?
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towr
wu::riddles Moderator Uberpuzzler
Some people are average, some are just mean.
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Re: new york times problem solving test
« Reply #4 on: Sep 1st, 2015, 10:15pm » |
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I can't remember how many "no"s I tried for. But after the initial "successive powers of two" phase I did test for "geometric sequence", "anything goes", "strictly monotonically increasing", "weakly monotonically increasing", "strictly monotonic", "weakly monotonic".
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Wikipedia, Google, Mathworld, Integer sequence DB
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rmsgrey
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Re: new york times problem solving test
« Reply #5 on: Sep 2nd, 2015, 9:02am » |
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on Sep 1st, 2015, 6:56pm, JiNbOtAk wrote:So, how many of us intentionally tried getting a "No" ? How many "No"s did you try to get before you were satisfied with the 'rule' ? |
| It's been a while since I first came across it, but I got something like 4 "no"s before settling on "strictly increasing numbers" with a general approach of trying to find boundaries between "yes" and "no" rather than trying to get easy "yes"es
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rloginunix
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Re: new york times problem solving test
« Reply #6 on: Sep 2nd, 2015, 10:20am » |
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I've got at least 4 "no"s: tried reversing the sequence as 8, 4, 2. Then 3, 9, 27. Then 27, 9, 3. Then rearranging the numbers: 4, 8, 2 and 9, 27, 3 etc. I think that on this forum you are dealing with, in general, a rather specific bunch: as a C(Java) Solaris/CentOS programmer I can say that codewise - especially the more you move away from the raw academic compsci code - before you get to a "yes" and return you step through a fair amount of "no"s and after a while it's in our blood. My family sometimes calls me "doom and gloom". Well. It's not doom and gloom. If it can go wrong - it will. So it's error/edge/boundary conditions/special cases handling ...
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Grimbal
wu::riddles Moderator Uberpuzzler
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Re: new york times problem solving test
« Reply #7 on: Sep 3rd, 2015, 7:19pm » |
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I did not start with what I should have, i.e. a global approach of searching yesses and nos. Instead, I saw the pattern 2k and tried to generalize it. I tried a*2k and a*bk. Only then I tried sequences that don't translate to a closed formula. I quickly accepted "strictly increasing" because I realized the point of the exercise was best made with the simplest rule and monotonic was the simplest I could think of. I checked whether it is strictly increasing or not. One explanation of what happens would be that we are usually asked to recognize a sequence. Once the idea of "powers of two" came to us, we have to first kill that idea before searching more globally.
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