cslarsen

/*
 * Print all permutations of string ``s´´. (C++)
 *
 * Solved as a counting problem and coded in a hurry.
 * 
 * A more elegant and recursive solution:
 * http://nicolas-lara.blogspot.com/2009/01/permutations.html
 */

#include <stdio.h>

cslarsen

/*
 * Reverse singly linked list. (C)
 *
 * Written in a hurry after reading this HN thread:
 * http://news.ycombinator.com/item?id=1471988
 * 
 */

#include <stdio.h>
#include <stdlib.h>

cslarsen

/*
 * Find the longest palindrome in the text.
 *
 * This is Greplin's first challenge, and I originally solved it in Python.
 *
 * The algorithm is not optimal, but simple on the eyes and easy to understand
 * On big inputs it's possible to use an approximately linear algorithm.
 *
 * Christian Stigen Larsen
 */

cslarsen

/*
 * Find the longest palindrome in the text.
 *
 * This is Greplin's first challenge, and I originally solved it in Python.
 *
 * This algorithm is linear on the average input, but has a quadratic
 * worst case running time.  There exists an even better algorithm, but
 * this should do.
 *
 * There might also be a small error below, but you get the general idea.

cslarsen

/*
 * A simple sieve of Eratosthenes using bitsets, written by Christian Stigen Larsen
 * You are free to use this code for anything (i.e., public domain).
 */

#ifndef INC_PRIMES_H
#define INC_PRIMES_H

#include <vector>
#include <algorithm>

cslarsen

/*
 * FizzBuzz
 */

#include <stdio.h>

char* bits(int n)
{
  #define BITS 8
  #define BIT(x) (x? '1' : ' ');

cslarsen

In "Reflections on trusting trust" --- http://cm.bell-labs.com/who/ken/trust.html --- Ken Thompson urges the reader to try write a quine. If you haven't done so yet, please try before reading on.

Here are two quines I made (without cheating), loosely based on the same idea, that I wrote in C. The first one is macro-based, utilizing the ability for macros to quote parameters:

#define Q(x) #x;x
char *q=Q(main(){printf("#define Q(x) #x;x\nchar *q=Q(");printf(q);printf(")\n");})

Compiling and running it produces an exact copy of itself:

~/devel/quine csl$ gcc --no-warnings shortq.c -o shortq && ./shortq

cslarsen

#!/usr/bin/env python
# -*- coding: iso-8859-1 -*-

"""
Written by Christian Stigen Larsen, http://csl.sublevel3.org
Placed in the public domain by the author

This is a version of the classic game of guessing which animal you
are thinking about.  It uses a binary tree to guess.

cslarsen

% MetaPost free body diagram with frictional forces
%
% Placed in the public domain by the author; Christian Stigen Larsen
% 2011-10-07
%
% To render:
% $ mptopdf free-body.mp
%

  beginfig(1)

cslarsen

/*
 * A simple sieve of Eratosthenes using bitsets, written by Christian Stigen Larsen
 * You are free to use this code for anything (i.e., public domain).
 *
 * This sieve allocates the bitset on the heap, so you can calculate a lot
 * of prime numbers.
 */

#ifndef INC_PRIMES_H
#define INC_PRIMES_H