February 2020 Archives

Perl Weekly Challenge 048: Survivor and Palindrome Dates


There are 50 people standing in a circle in position 1 to 50. The person standing at position 1 has a sword. He kills the next person i.e. standing at position 2 and pass on the sword to the immediate next i.e. person standing at position 3. Now the person at position 3 does the same and it goes on until only one survives.
Write a script to find out the survivor.

I tried two different approaches to the problem.

The first one uses an array of living people and a variable $sword that stores the index of the person holding the sword. In each iteration of the loop, the next person is removed from the array, and the sword is passed to the next person.

The “next person” has a special cyclic meaning: at the end of the array, the sword must return to the beginning. This is achieved by using the modulo operator %. Note that we use it twice, once to find the person to kill, and once to find the person to pass the sword to—and each case uses a different array size in the modulo operation, as killing a person changes the size of the array.

Perl Weekly Challenge 046: Cryptic Message & Is the Room Open?

Cryptic Message

The communication system of an office is broken and message received are not completely reliable. To send message Hello, it ended up sending these following:
H x l 4 !
c e - l o
z e 6 l g
H W l v R
q 9 m # o

Similarly another day we received a message repeatedly like below:

P + 2 l ! a t o
1 e 8 0 R $ 4 u
5 - r ] + a > /
P x w l b 3 k \
2 e 3 5 R 8 y u
< ! r ^ ( ) k 0

Write a script to decrypt the above repeated message (one message repeated 6 times).

Even without reading the hint, the idea seems clear: for each column, the output should consist of its most frequent character. As usually, to count frequency, we’ll use a hash. To find the most frequent one, we’ll use max from List::Util.

About E. Choroba

user-pic I blog about Perl.