pseudocode of zigzag conversion

1.Title : 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".

2.pseudocode : 

 creat data structure:
     the given number of rows  →  nRows;
     the given text string  →  s;
     stringBuffer[] to restore result  →  sb;
 set char position index i = 0;row position index j = 0;combing outcome index k = 1;
 while i < the length of s,then
     for each j from 0 to (nRows - 1)
         append the ith char of s to sb[j];
         i++;
     end
     for each j from (nRows - 2) to 1
         append the ith char of s to sb[j];
         i++;
     end
 end
 //form a united outcome
 for each k from 1 to (nRows - 1)
     append sb[k] to sb[0];
 end
 terminate and output sb[0];