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
deepak garg: 2015-10-03 13:39:08

what if the message to be encrypted has 'x's in last too? e.g string is " this is string for example xyxx"

lagboy: 2015-09-18 23:27:14

If you're using py 2.7.10, don't forget to append a newline before you start each new test case or it throws a WA.

shantanu tripathi: 2015-08-12 19:41:03

quite esy one... :)

sahil_agarwal: 2015-07-17 14:57:53

Consider the comment by @_R0b_ if you need help
My 50th :)

Coder: 2015-06-26 16:52:15

should i have to output one by one?or take input first and output for every test case plz someone help...

sriramadabala: 2015-06-14 13:12:54

Don't forget that output should be printed in one line

dr_strange: 2015-05-22 20:53:15

getting SIGSEV here but the code works fine on the terminal

kobe24: 2015-05-15 07:35:59

thanks i forgot newline

erdi_1991: 2015-04-05 17:47:29

Where can i see the Test Cases?

_R0b_: 2015-03-16 16:22:26

you can solve this problem if you can solve the below pattern
n = 3
0 1 2
5 4 3
6 7 8
11 10 9 and so on . . . . up to string len . . .

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