If we write $\displaystyle F(x) = \sum_{n=0}^\infty f(n)x^n$, then we have
$$f(n-1) + f(n+1) = kf(n)$$
$$\sum_{n=0}^\infty f(n-1)x^n + \sum_{n=0}^\infty f(n+1)x^n = kF(n)$$
$$\sum_{n=-1}^\infty f(n)x^{n+1} + \sum_{n=1}^\infty f(n)x^{n-1} = kF(x)$$
$$f(-1)+\sum_{n=0}^\infty f(n)x^{n+1} -f(0)x^{...
(inspired by this post over on Puzzling. CAUTION: SPOILERS FOR THAT PUZZLE ARE BELOW.)
The standard telephone keypad correlates letters to numbers as follows:
1 ->
2 -> ABC
3 -> DEF
4 -> GHI
5 -> JKL
6 -> MNO
7 -> PQRS
8 -> TUV
9 -> WXYZ
0 ->
A given input word is defined to be an Ordered Wor...
This is a list of unofficial, deadline-less (hence not searchable) bounties offered by users on various challenges on the main site.
Disclaimer: There is no guarantee that the user will award the bounty for you in case you fulfill its requirement. Especially if the user isn't an active member an...
Python 2, 164 148 132 77 bytes
-16 bytes thanks to Rod's suggestion elsewhere. A frickin' -55 bytes thanks to Arnold Palmer.
n=[min(int((ord(i)-58)/3.13),9)for i in input()]
print sorted(n)in[n,n[::-1]]
Try it online!
Input must be uppercase. Outputs True or False based on its orderedness.
Pyth, 29 bytes
KmhS+9]/-Cd58 3.13w|qKSKqK_SK
Test Suite.
We are going to fold a list of integers. The procedure to do so is as follows, If the list is of even length, make a list of half of its length where the nth item of the new list is the sum of the nth item of the old list and the nth-to-last item of the old list. For example if we had the list...
As some of you may know, to get a language onto Dennis's wonderful Try It Online!, a Hello, World! program is required. Recently, Dennis pushed up a way to load these programs from the website. Here is a JSON pastebin of the characters used in those programs, by frequency, as of July 27, 2017.
S...
I saw Tom Scott's video on FizzBuzz https://www.youtube.com/watch?v=QPZ0pIK_wsc
so I felt to write my own more "complex" version,this is what I came up with, its very flexibly and easy to scale, and its easy to add more if cases that can trigger functions.
Code(C# console application):
// FizzB...
Based on random source code:
def randint(a, b):
"Return random integer in range [a, b], including both end points."
return a + randbelow(b - a + 1)
def randbelow(n):
"Return a random int in the range [0,n). Raises ValueError if n<=0."
if n <= 0:
raise ValueError
k = ...
Several questions have recently been asking about random. I see a lot of answers in those questions using the date not as a seed but as the random number that is then modulo'ed.
Seen in Java:
System.currentTimeMillis()%N
System.nanoTime()%N
Seen in JavaScript:
new Date%N
Doing so is random...
Generate a Spiral Matrix
Related: Print NxN spiral of ascending numbers - This challenge is meant to replace that old challenge by covering all spiral matrices.
Given N, generate one out of all the spiral matrices with dimensions N x N using the values [0, 1, ..., n-1].
For example, if N = 5...
What's my name? code-golf internet
Given a PPCG User ID, output that user's current username.
Examples
Input -> Output
65535 -> MD XF
2 -> Geoff Dalgas
12012 -> Dennis
foo ->
-3 ->
Rules
Input/output can be taken via any allowed means.
The output must be the full username with p...
Task: Output the Swiss flag.
Happy Swiss National Day / Schweizer Bundesfeiertag / Fête nationale suisse / Festa nazionale svizzera / Fiasta naziunala svizra!
Details:
The flag consists of a white (#FFFFFF) cross on a red (#FF0000) background. The cross consists of a 6x6 square with arms of s...
