ZigZag Conversion

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".

 

public class Solution {
    public String convert(String s, int numRows) {
        String[] v = new String[numRows];
		Arrays.fill(v, 0, numRows, "");
		for (int i = 0; i < s.length();) {
			for (int j = 0; i < s.length() && j < numRows; ++i, ++j)
				v[j] += s.charAt(i);
			for (int j = numRows - 2; i < s.length() && j > 0; ++i, --j)
				v[j] += s.charAt(i);
		}
		String res = "";
		for (int i = 0; i < numRows; ++i)
			res += v[i];
		return res;
    }
}