problem：
The string "PAYPALISHIRING" is written in a zigzag pattern on a given number
of rows like this:
(you may want to display this pattern in a fixed font for better legibility)
P A H N
A P L S I I G
Y I R
And then read line by line: "PAHNAPLSIIGYIR"
Write the code that will take a string and make this conversion given a
number of rows:
string convert(string text, int nRows);
convert("PAYPALISHIRING", 3) should return "PAHNAPLSIIGYIR".The string "PAYPALISHIRING" is written i
