Submission Details(Better Solution)

public class Solution {
    public String convert(String s, int nRows) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        assert(s != null);
    if (nRows == 1) return s;

    StringBuffer buf = new StringBuffer();
    int diff = nRows + nRows - 2;
    for (int i = 0; i < nRows; i++) {
        int index = i;
        while (index < s.length()) {
            buf.append(s.charAt(index));
            index += diff;
            if (i != 0 && i != nRows - 1 && index - i - i < s.length()) {
                buf.append(s.charAt(index - i - i));
            }
        }
    }

    return buf.toString();
    }
}