Obfuscated hello world! (perl regex powered)

mauro — Wed, 06 Jun 2007 15:18:21 +0000

¿Cuáles son las 10 primeras cifras consecutivas no repetidas de los decimales de PI?
4592307816

echo "scale=100;a(1)*4" | bc -l | sed ':a;N;s/\\\n//;ta' | \
perl -pe 's/.*?(.)(?!\1)(.)(?!\1|\2)(.)(?!\1|\2|\3)(.)(?!\1|\2|\3|\4)(.)(?!\1|\2|\3|\4|\5)(.)(?!\1|\2|\3|\4|\5|\6)(.)(?!\1|\2|\3|\4|\5|\6|\7)(.)(?!\1|\2|\3|\4|\5|\6|\7|\8)(.)(?!\1|\2|\3|\4|\5|\6|\7|\8|\9)(.).*/$1$2$3$4$5$6$7$8$9$10/'

¿Dónde en las cifras de PI está escondida la frase ‘Hello world’?
21463853067

Pues

$ echo 21463853067 | tr 0-9 reHolwld\
Hello world
$

echo "scale=4721;a(1)*4" | bc -l | sed ':a;N;s/\\\n//;ta' | \
perl -pe 's/.*?(.)(?!\1)(.)(?!\1|\2)(.)(?!\1|\2)(.)(?!\1|\2|\3|\4)(.)(?!\1|\2|\3|\4|\5)(.)(?!\1|\2|\3|\4|\5|\6)(.)(?!\1|\2|\3|\4|\6|\7)(.)(?!\1|\2|\3|\4|\5|\6|\7|\8)(.)(?!\1|\2|\5|\6|\7|\8|\9)(.)(?!\1|\2|\3|\4|\5|\6|\7|\8|\9|\10)(.).*/$1$2$3$4$5$6$7$8$9$10$11/' | \
tr 0-9 "reHolwld "

O, para el debianita impaciente:

sudo apt-get -y install pi >/dev/null && pi 4721 | \
perl -pe 's/(.)(?!\1)(.)(?!\1|\2)(.)(?!\1|\2)(.)(?!\1|\2|\3|\4)(.)(?!\1|\2|\3|\4|\5)(.)(?!\1|\2|\3|\4|\5|\6)(.)(?!\1|\2|\3|\4|\6|\7)(.)(?!\1|\2|\3|\4|\5|\6|\7|\8)(.)(?!\1|\2|\5|\6|\7|\8|\9)(.)(?!\1|\2|\3|\4|\5|\6|\7|\8|\9|\10)(.).*/$1$2$3$4$5$6$7$8$9$10$11/' | \
tr 0-9 "reHolwld "

Now that we have pi installed, we can venture further:

pi 62999 | tr 0-9 del\ l\!owrH

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Obfuscated hello world! (perl regex powered)