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.






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ayaan2525: 2018-10-02 12:22:23

AC in one go..:-)
solved using matrix

akshaykumar17: 2018-09-27 15:18:28

first attempt :), Not so easy but implement properly and instead of matrix one can use strings also which will take less time.

purici_marius: 2018-09-24 22:23:35

Finally solved it!!! No matrix required !

probeta: 2018-08-29 18:39:30

Finally solved it ! Just write it on paper .

n1trob4ct3r: 2018-08-25 19:54:23

AC in one go without using grids.

rishabh_jiit: 2018-08-24 20:09:25

Ac in a single go !! Quiet easy question if you just draw a index map on a rough paper for your reference.
No Matrix Needed!

kranthi_0003: 2018-08-11 08:20:05

AC in one go..;)

suyashky: 2018-07-22 14:38:46

loop 1:
consider chars in pair of n (no of col)
swap chars within alternate pairs

loop 2:
print as the pattern required
(see the obtained string after loop 1 to get pattern)

Last edit: 2018-07-22 14:39:15
hello_world123: 2018-06-21 18:36:39

Only 1% of the people would have solved without matrix.
No one takes the tough path.

jeet9: 2018-06-09 08:35:52

First Attempt - All GREEN ;)

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