# Tagged Questions

This tag exists for historical reasons. New questions of the type previously posted under this tag are not welcome.

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### You call this optimized? [closed]

The task is simple, post 2 code snippets that perform the same task, where one seems very optimized at first glance, but actually is significantly slower than the other. Only one rule: Both ...
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### Like a quine, but not [closed]

Very simple, write a program that at first glance appears to be a quine, but is not. Upon running, the program actually prints the source to a real quine, obviously distinct from the original program ...
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### Classic Proof Fallacy [closed]

The Background So, we all know the classic proof that goes like this: a = b a² = ab a² - b² = ab - b² (a-b)(a+b) = b(a-b) (a+b) = b b+b = b 2b = b 2 = 1 (Ha ha!) Of course, the mistake is that ...
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### Quiche Lorraine [closed]

Since it was Pi day recently, I have noticed a number of challenges that ask you to calculate pi. Of course, a quiche lorraine is not quite a pie (you can claim a Bonus Score¹ of +1 if you guessed ...
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### Recognize Twin Primes by Crashing [closed]

Background Story Bob was handed the following assignment for his programming class. Please note: this is not the actual challenge. Homework assignment 11: Twin primes Input: an integer n ≥...
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### Confuse the Dakotas

You have been hired by the government of North Dakota to encrypt the state's communications. Write two programs, one to encrypt a message and one to decrypt that message. The government is not really ...
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### Break Stack Exchange [closed]

Trick the user that StackExchange is broken: It can be done in several ways: Your program starts a browser in some certain way (with a proxy server, for example); Your program shows static ...
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### Sabotage the coding standards [closed]

There are various coding standards enforced at software companies which have the goal of increasing code reliability, portability, and, most importantly, readability in code written jointly by ...
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### Sabotage a Train to Make It Run Late

"I want to go to the Araby bazaar to buy a present for the one I have fallen in love with. However, if I arrive too late all the stores will be closed and I won't be able to buy anything. Can you help ...
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### Underhanded Bank Account [closed]

You are working as a programmer for a bank. Your task is to write a program that handles the transactions from one bank account to another. The program should do the following: Run in an infinite ...
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### Start a revolution in Oceania

Winners (decided 14/09/14) Winning answer by Markuz (Python) - 63 votes Runner up by kuroi neko (PHP) - 55 votes Introduction You are in the world of the book Nineteen Eighty-Four by George Orwell....
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### Print all multiples of 32 from 0 to `n`…imperfectly [closed]

Objective: Print all multiples of 32 from 0 to an arbitrary number n. Rules: One argument will be given: a single integer from 0 to 231 - 1. This will be n here on out. The first iteration must be ...
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### Break out of a loop [duplicate]

Now that we have over a hundred ways to get stuck in a loop, the next challenge is to get out. Specifically, write a piece of code with a (seemingly) infinite loop, but somehow manage to break out. ...
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### Implement `map()`…with bugs [closed]

EDIT: The behavior may be inconsistent. Also, associative arrays are permitted. Make a function that iterates through an indexed array, mapping a function of a single argument to each member of the ...
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### Fake infinite loop [closed]

The challenge is to write a fake infinite loop in any imperative programming language. At first sight, the code should seem not to halt at all. As a naive example: int f(int x) { return f(4.0); ...
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### “Disprove” Fermat's Last Theorem [closed]

Write a program, in the language of your choice, that appears to successfully find a counterexample to Fermat's Last Theorem. That is, find integers a, b, c > 0 and n > 2 such that an + bn = cn. Of ...
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### It's not who votes that counts; it's who counts the votes [closed]

The scenario You live in a country that is having a presidential election. Each voter gets one vote, and therefore there is a firmly-entrenched two-party system. (Third parties exist, but get ...
18k views

### Random script that isn't actually random

As a little joke in the office someone wanted a script that randomly picks a name, and said person will make a round of drinks. Let's call the people John, Jeff, Emma, Steve and Julie. I thought it ...
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### Deletion of a blank line in source code which causes unexpected functionality [closed]

Write a script that works fine when a blank line is present in the flow of program logic, but breaks or causes unexpected behaviour when that line is removed. Avoid standard loopholes and stupid ...
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### Efficient error-free* encoding [closed]

The mission As is well known, the genetic material of all known creatures on Earth is encoded in DNA; using the four nucleotides adenine, thymine, cytosine, and guanine. (Commonly represented by ATGC)...
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### Make it look like I'm working

Often, I find myself running a script or query that will take a significant amount of time to run. I can leave that script open and enjoy some guilt-free procrastination. Now, what if I could write ...
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### Write a sorting program that looks erroneous but it is actually correct [closed]

Write a program that sorts a vector of numbers (or any type of element) that looks like having one or more bugs, but it is actually ok. The code must be clear. Someone looking over the code must ...
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### Produce an unexpected word [closed]

The goal is to write program that will produce a word unexpectedly (program doesn't look like it is going to produce a word). Example (JavaScript): alert(([0][1]+"").slice(4,8)) Explanations: ...
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### Pi is still wrong [closed]

Pi is Wrong A common method of computing pi is by throwing "darts" into a 1x1 box and seeing which land in the unit circle compared to the total thrown: loop x = rand() y = rand() if(sqrt(x*...
179k views

### Write a program that makes 2 + 2 = 5 [closed]

Write a program that seemingly adds the numbers 2 and 2 and outputs 5. This is an underhanded contest. Your program cannot output any errors. Watch out for memory holes! Input is optional. ...
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### Program that adds all natural numbers and yields -1/12 [closed]

As you might know there is a mathematical fun-fact that if you add all natural numbers you end up with... -1/12 (see Wikipedia here). Of course this is very strange result and can not be obtained by ...
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### Throw a null-pointer exception

Your task is to generate a null-pointer exception. That is, your program must accept a value which it expects to be non-null, and throw an exception/error or crash because the value is null. ...
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### Pathological Sorting

Pathological Sorting Your boss has demanded that you develop a sorting algorithm to improve the performance of your company's application. However, having written the application, you know that you'...
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### Cheap, Fast, Good - Common Factor (Greatest) [closed]

Inspired by Cheap, Fast, Good, we're going to implement an algorithm which has exactly two of them. The Math Given two nonzero integers a and b, the GCF d is the largest integer that divides both a ...
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### Underhanded contest (?): Anti-Virus wars [closed]

Prove anti-virus software is paranoid by making a program that simply opens and alphabetically sorts a CSV file, that will get flagged as a virus (or malware/spyware/any threat really) when run. You ...
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### So obviously, P = NP [closed]

SAT is the problem of determining whether a boolean expression can be made true. For example, (A) can be made true by setting A=TRUE, but (A && !A) can never be true. This problem is known to ...
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### Why isn't it ending? [closed]

Your task: To write a program that should obviously terminate, but it never (to the extent of a computer crash) does. Make it look like it should perform a simple task: adding numbers, printing ...
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### Obfuscation Challenge [closed]

You are to write a program that does one of the following. Only displays "Hello World" does nothing else Quits and nothing else (no output, no errors.) Takes one line of input, parses it as an ...
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### Trolling the troll [closed]

A troll has captured you and is forcing you to write malware (defined as a program that damages the computer that runs it). The troll can read and understand code, but is not so good at spotting bugs. ...
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### These are my lucky dice

Implement a program or function which simulates common dice for role playing games. It should handle at least the d6 and d20, the two most common dice. However, it should work as stereotypical gamers ...
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### What? No error? [closed]

Your task is simple. Write a program that should obviously produce an error on first glance either when compiled or run, but either doesn't or produces some other unrelated error. This is a popularity ...
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### Loophole for other challenge [closed]

You are to post an answer you posted that exploited a loophole in the challengers question. Bonus points if it caused them to rewrite the question. For example, one challenge was to write a program ...
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### Underhanded code contest: Not-so-quick sort [closed]

The Task Write a program, in the language of your choice, that reads lines of input from standard input until EOF, and then writes them to standard output in ASCIIbetical order, similar to the sort ...
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### Write a line in program that looks useless [closed]

Write some program (the size doesn't matter), and put a line that looks useless, but it's actually not - if it would be removed, the program would crash, or do something wrong. Feel free to mark the ...
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### Find the largest prime under a number… but only for the test cases [closed]

The Code Your program should take an input of n > 2 and output the largest prime less than or equal to n. You can choose how the number is input (standard input, read from a file, etc). For example: ...
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### Hide evil code - print files containing a given string anywhere in a directory tree [closed]

The point of this puzzle is to learn how a malicious code can be hidden and discovered in a program. A person is asking the question: Plz give me some code that how can I search a file may be in ...
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### An unintentional-looking but crash-causing bug [closed]

There are a range of questions revolving around this concept, but these all seem to just involve causing a crash, resulting in many answers which are very obviously designed to cause a crash. So the ...
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### Challenge: Write a piece of code that quits itself [closed]

I'm searching (am I?) for a piece of code that quits immediately - in an absolutely unconventional way. This does not mean: System.exit((int) 'A'); (Java). It might mean: #!/usr/bin/env python3 # ...
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### Write a java code to detect the JVM version [closed]

The objective is to write java code that detects the JVM version relying in compatibility changes, side effects, bugs and/or undefined behavior that works in a way in one version and another way in ...
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### Underhanded launcher [closed]

Your goal is to write a super-secret program which launches another (independent) program. You don't have to provide the payload in your answer, it can be any program name your program will launch. ...