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Computational complexity of Fibonacci Sequence

I understand Big-O notation, but I don't know how to calculate it for many functions. In particular, I've been trying to figure out the computational complexity of the naive version of the Fibonacci sequence: ...
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Using a dispatch_once singleton model in Swift

...ants (and variables), and is thread safe by the definition of let. This is now officially recommended way to instantiate a singleton. Class constants were introduced in Swift 1.2. If you need to support an earlier version of Swift, use the nested struct approach below or a global constant. Nested ...
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Is there a way to create xxhdpi, xhdpi, hdpi, mdpi and ldpi drawables from a large scale image?

...time (downside: will only work on fairly recent devices, where -xxhdpi is known). Option #2: Use Android Asset Studio to downsample them for you. Option #3: Automate the process within a graphics editor, per ssantos' answer. Option #4: Script yourself a solution, using something like ImageMagick. Op...
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Simpler way to put PDB breakpoints in Python code?

... whatever other languages you use. 2019 Update (Python 3.7+) Python 3.7+ now has the builtin breakpoint() which can replace the previous import pdb; pdb.set_trace() in vim. It still works the same. share | ...
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Git and nasty “error: cannot lock existing info/refs fatal”

... I've added some background info, but I must honestly say I don't know exactly why and how this works :) – arno_v Jan 12 '18 at 7:36 1 ...
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Difference between freeze and seal

... FWIW, frozen and sealed objects are now faster than their unfrozen and unsealed counterparts in Chrome Canary v43.0.2317.0. – llambda Feb 28 '15 at 22:57 ...
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Ruby optional parameters

...s = nil) scope ||= LDAP::LDAP_SCOPE_SUBTREE ... do something ... end Now if you call the method as above, the behaviour will be as you expect. share | improve this answer | ...
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How to delete an app from iTunesConnect / App Store Connect

...o do is delete that app completely from my itunesconnect account. I don't know what apple recently changed but in the past once the app was rejected I use to see a "delete" button on the summary page. Now I don't see one anymore. ...
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Stashing only staged changes in git - is it possible?

...king directory (still in state staged). Run git stash push -m "good stash" Now your "good stash" has ONLY staged files. Now if you need unstaged files before stash, simply apply first stash (the one created with --keep-index) and now you can remove files you stashed to "good stash". Enjoy ...
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Swift: Convert enum value to String?

... Not sure in which Swift version this feature was added, but right now (Swift 2.1) you only need this code: enum Audience : String { case public case friends case private } let audience = Audience.public.rawValue // "public" When strings are used for raw values, the implic...