Write a program that makes 2 + 2 = 5

123 点作者 bryan_rasmussen将近 11 年前

26 条评论

Kenji将近 11 年前

I would like to post on there but it's protected from people with low reputation... Maybe someone here appreciates my solution in C:<pre><code> #include <stdio.h> int main(int argc, char* argv[]){ int arr[1]; int a = 2; int b = 2; arr[1] = 3; printf("%d", a+b); return 0; } </code></pre> Explanation: I go out of bounds of the array arr, it only has one value but I access the second value. That's why b is likely to get overwritten with 3 and hence a+b=5

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Clex将近 11 年前

Here's mine :<pre><code> $ cat test.c #include <stdio.h> int main() { int a = 3; int b = 3; // aren't we supposed to add 2 and 2 ??/ a = 2; b = 2; printf("%d\n", a + b); return 0; } $ gcc -W -Wall -trigraphs test2.c 2>/dev/null $ ./a.out 5 $</code></pre>

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userbinator将近 11 年前

That Java one is particularly amusing, as most programmers otherwise familiar with the language would never know about the integer cache (and their reaction upon discovering that there is one would probably be the same as mine - WTF?)Edit: I had a feeling I'd heard of an "integer cache" somewhere else" in a WTF-eliciting context... <a href="http://thedailywtf.com/Articles/The-Integer-Cache.aspx" rel="nofollow">http://thedailywtf.com/Articles/The-Integer-Cache.aspx</a> !

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Lockal将近 11 年前

UB abuse in C/C++ Linux x86-64 (works with gcc/clang/icc with any optimization level):<pre><code> #include <stdio.h> int main() { double x; printf("Input any number:\n> "); if (scanf("%lf", &x) == 1) { printf("Is 2 + 2 really equals %g? Let's try!\n", x); printf("2 + 2 = %g\n", 2 + 2); } else { printf("Invalid input!\n"); } } </code></pre> Output:<pre><code> Input any number: > 5 Is 2 + 2 really equals 5? Let's try! 2 + 2 = 5 </code></pre> Explanation: linux x86-64 calling convention uses xmm registers to pass fp values. In the first printf we initialize %xmm0 with some value. In the second printf we put integer 4 in %esi, however printf reads value again from %xmm0. Here is an assembly in GCC explorer (sorry for shortened link, that's how GCC explorer works): <a href="http://goo.gl/mY9phE" rel="nofollow">http://goo.gl/mY9phE</a>

yiedyie将近 11 年前

JavaScript ;)<a href="http://codegolf.stackexchange.com/a/29944/12328" rel="nofollow">http://codegolf.stackexchange.com/a/29944/12328</a>

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rkowalick将近 11 年前

Here's a Ruby solution that really does modify the + operation:<pre><code> class Fixnum alias_method :old_plus, :+ def +(*args) old_plus(*args).old_plus(1) end end 2 + 2 #=> 5</code></pre>

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im3w1l将近 11 年前

<pre><code> public class Main { public static void main (String [] args) { System.out.println("‮5=2+2‭"); // prints ‬4=2+2 } }</code></pre>

comex将近 11 年前

C:<pre><code> #include <stdio.h> #include <stdbool.h> #include <stdlib.h> int nums[5] = {1, 0, 1, 0, 1}; static int cur; int main(int argc, char **argv) { for(int i = 1; nums[i] != 5 && i < 10; i++) { cur = i; if(i/4 == 1) { printf("2 + 2 <= %d = %s\n", cur, 2 + 2 <= i ? "true" : "false"); printf("2 + 2 == %d = %s\n", cur, 2 + 2 == i ? "true" : "false"); printf("\n"); } } } </code></pre> No strange array writes! No indirect writes at all!It's finicky and I believe depends on register allocation, but when I compile it using whatever version of gcc-mp-4.9 I have installed from MacPorts at -O3, it outputs, among other things:<pre><code> 2 + 2 == 5 = true </code></pre> (For all they say about evil optimizing compilers, it was really hard to make this work.)

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dgl将近 11 年前

Because I can't post on stackoverflow either, here's my variant in C (requires glibc, and a deprecated function at that).<pre><code> #include <printf.h> #include <stdio.h> #include <string.h> int d_cb(FILE *stream, const struct printf_info *info, const void *const* args) { int num = (*(int*)(((int**)args)[0])), numw = info->width; char str[10], numn = num|numw, *out = str; num = num < 0 ? *out++ = '-', -num : numn; do { *out++ = '0' + num % 10; num /= 10; } while(num); fwrite(str, out - str, 1, stream); return 0; } void init() { register_printf_function('d', d_cb, 0); } int main() { init(); printf("2+4 = %d, 2+2 = %1d\n", 2+4, 2+2); return 0; }</code></pre>

masak将近 11 年前

Here's the Perl 6 solution:<pre><code> multi infix:<+>(2, 2) { 5 } say 2 + 2; # 5</code></pre>

charles2013将近 11 年前

Ruby solution (don't have enough rep to post to codegolf):<pre><code> def mad_addr(a,b) a == b && a == 2 ? (a.object_id + b.object_id)/a : a + b end </code></pre> Explanation: If a and b are both equal to 2 we can sum the values of the object_id's (the object_id of 2 is 5), and then divide the sum by 2. [Edit to add] For all other numbers this should behave as expected.I just learned the object_id of 2 is 5 while doing this exercise, and I would like to continue learning more about how Ruby works. So if you have feedback, criticisms, or other ideas regarding this solution please feel free to share :)[edit: added missing `=`]

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X4将近 11 年前

Asking: Isn't the only true solution the one using Decibels for Addition? Because everyone else either just redefines or overwrites a value. Also addition of decibels cannot be disproofed as fake.

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anon4将近 11 年前

You know, this would be possible in C and C++ if you add some code at the start of main() that unprotects the executable section, goes through it and modifies each "load 4 in register X" instruction to "load 5", then forks a process that attaches itself as a debugger to the executable to monitor every add and change the result to 5 if it's 4.

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whoopdedo将近 11 年前

Lua:<pre><code> local debug = require "debug" -- in case 5.2 debug.setmetatable(1, {__tostring=function(n) return ("%g"):format(n+1) end}) print(2+2) </code></pre> Trying to make 2+2==5 evaluate as true is a lot harder. Although Lua lets you define a custom + operator, it's a fallback not an override.

Too将近 11 年前

How about the opposite? Make 2+3=4, here in C.<pre><code> add2And3(int *a, int *b) { *a = 3; *b = 2; printf("%d", *a + *b); //4 } void main() { int storage; add2And3(&storage, &storage); }</code></pre>

isivaxa将近 11 年前

<pre><code> #!/bin/bash tty if [[ $? -ne 0 ]] ; then # command returned nonzero echo "not a tty" else # command returned zero n=$? ((n=$n+2)) ((n=$n+2)) echo "0+2+2=$n"; fi</code></pre>

Datsundere将近 11 年前

Haskell:<pre><code> let 2 + 2 = 5</code></pre>

social_monad将近 11 年前

Simple solution in R:<pre><code> > '%+%' <- get( '+') > '+' <- function( e1, e2) 1 %+% e1 %+% e2 > 2+2 [1] 5 </code></pre> Regards

howeman将近 11 年前

Combining a couple ideas, here's a Go solution<a href="http://play.golang.org/p/XnPglbkLW4" rel="nofollow">http://play.golang.org/p/XnPglbkLW4</a>

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gdewilde将近 11 年前

You have to add 1 to either the first or the second 2 or to the sum of the two.

terranera将近 11 年前

#lang racket (define (add-bizzare x y) (round (+ (+ x 0.4) (+ y 0.4))))

diego将近 11 年前

My first thought in Clojure.<pre><code> (let [+ (partial + 1)] (+ 2 2))</code></pre>

NaNaN将近 11 年前

The JavaScript answer from @user1886419 is a great joke. lol

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runarberg将近 11 年前

Julia<pre><code> !(a::Int) = !bool(a) !0 + 2 + 2 ##> 5</code></pre>

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san86将近 11 年前

why not just overload the + operator in C++?

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noobermin将近 11 年前

I'm surprised no one has suggested this yet. In python>Write a program that seemingly adds the numbers 2 and 2a=2+2>and outputs 5.print(5)Yeah, I know that isn't the intent here, but, following the wording of the contest rules exactly...