TOANDFRO - To and Fro

Mo and Larry have devised a way of encrypting messages. They first decide secretly on the number of columns and write the message (letters only) down the columns, padding with extra random letters so as to make a rectangular array of letters. For example, if the message is “There’s no place like home on a snowy night” and there are five columns, Mo would write down

t o i o y
h p k n n
e l e a i
r a h s g
e c o n h
s e m o t
n l e w x

Note that Mo includes only letters and writes them all in lower case. In this example, Mo used the character ‘x’ to pad the message out to make a rectangle, although he could have used any letter. Mo then sends the message to Larry by writing the letters in each row, alternating left-to-right and right-to-left. So, the above would be encrypted as


Your job is to recover for Larry the original message (along with any extra padding letters) from the encrypted one.


There will be multiple input sets. Input for each set will consist of two lines. The first line will contain an integer in the range 2...20 indicating the number of columns used. The next line is a string of up to 200 lower case letters. The last input set is followed by a line containing a single 0, indicating end of input.


Each input set should generate one line of output, giving the original plaintext message, with no spaces.






hide comments
surfeyone: 2020-05-16 22:37:32

the input is the number of ROWS btw.
number of columns USED = rows
man I shouldve looked at the test case properly

saddy_2001: 2020-04-23 18:56:17

just store the given string in the 2D matrix then just reverse the odd index of the matrix and then iterate column wise.

trulyness: 2020-04-09 13:52:09

What are the vote requirements for SPOJ? What are the 15 needed problems?

mukulstriker: 2020-03-18 14:46:27

AC in one go don't make it complex its simple. Use array and it will work simply if you have any difficulty ask me as i am also a begginer in coding so i am happy with the result i got here will help you to.

anassk: 2019-12-27 19:12:54

runtime error (NZEC)
Standard input is empty you should give the input

mukesh_g7: 2019-12-16 04:51:22

getting a runtime error after the output is displayed.

thiyagumessi: 2019-12-09 09:49:19

Hint: make a list by breaking down given string with each length 5. use 2 loops one with n and other with the list and pront values.
also mriow has effecient solution

Last edit: 2019-12-09 09:51:52
gak: 2019-10-29 17:42:09

Too Easy! No need to use 2D array or stack.

black_spider1: 2019-10-25 03:36:15

AC in one go!

trhgquan: 2019-10-24 14:58:54

1 hit AC from Vietnam :D

Added by:Adrian Kuegel
Time limit:1s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Resource: ACM East Central North America Regional Programming Contest 2004