Code golf is a type of recreational computer programming competition in which participants strive to achieve the shortest possible code that solves a certain problem.
Source: Wikipedia
I've recently found some very interesting code golf examples on codegolf.stackexchange.com:
Snake
Task: Recreate the classic snake Game.
The shortest answer is written in Ruby in 316 characters, the longest is written in Java in 2239 characters.
Here is a Python answer with 818 characters:
import pygame as p
from random import randint as r
p.init()
l = 20
c = p.time.Clock()
dp = p.display
w = p.display.set_mode((500, 500))
C = p.Color
b = C(0, 0, 0)
g = C(0, 255, 0)
D = (0, 1)
U = (0, -1)
L = (-1, 0)
R = (1, 0)
S = [R]
d = R
n = []
O = lambda t: {U: D, R: L, D: U, L: R}[t]
def Q(e):
print("Score: %i" % (len(S) - 1))
p.quit()
def K(e):
global d
_ = {276: L, 273: U, 274: D, 275: R}.get(e.key, (0, 0))
d = not _ == O(d) and _ or d
def N(S):
[p.draw.rect(w, g, [x[0] * l, x[1] * l, l, l]) for x in S + n]
def M():
n = (r(0, 24), r(0, 24))
return n not in S and n or M()
A = lambda s, o: tuple(x + y for x, y in zip(s, o))
n = [M()]
while True:
w.fill(b)
[{12: Q, 2: K}.get(e.type, lambda e: e)(e) for e in p.event.get()]
if not (0 <= S[-1][0] < 25 and 0 <= S[-1][1] < 25) or A(S[-1], d) in S:
Q(e)
if A(S[-1], d) in n:
S.append(A(S[-1], d))
n = [M()]
else:
S.append(A(S[-1], d))
S.pop(0)
N(S)
dp.update()
c.tick(6)
Matrix determinant
Task: Calculate the determinant of a $n \times n$ matrix.
Solution in J (61 characters):
-/>([:+/#(([{.<:@[}.])[:*//._2,\2#])])&.>(|.;])".];._2[1!:1[3
Solution in Python (198 characters):
t = input()
e = enumerate
p = (
lambda t: t
and ((b + [a], j + i) for i, a in e(t) for b, j in p(t[:i] + t[i + 1 :]))
or [([], 0)]
)
print(
sum(
reduce(lambda t, (i, r): t * r[i], e(p), 1 - i % 2 * 2)
for p, i in p([t] + [input() for x in t[1:]])
)
)
Factorial
Task: Find the factorial of a number.
J (12 characters):
f=:*/@:>:@i.
Python (27 characters):
f = lambda x: 0 ** x or x * f(x - 1)
By the way, the shortest Java solution is 85 characters long^^.