composing-squared-strings

Composing squared strings

A squared string is a string of n lines, each substring being n characters long. We are given two n-squared strings. For example:

s1 = "abcd\nefgh\nijkl\nmnop" s2 = "qrst\nuvwx\nyz12\n3456"

Let us build a new string strng of size (n + 1) x n in the following way:

• The first line of strng has the first char of the first line of s1 plus the chars of the last line of s2.
• The second line of strng has the first two chars of the second line of s1 plus the chars of the penultimate line of s2 except the last char
• and so on until the nth line of strng has the n chars of the nth line of s1 plus the first char of the first line of s2.

Calling this function compose(s1, s2) we have:

compose(s1, s2) -> "a3456\nefyz1\nijkuv\nmnopq"
or printed:
abcd    qrst  -->  a3456
efgh    uvwx       efyz1
ijkl    yz12       ijkuv
mnop    3456       mnopq