LeetCode Online Judge-6. 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".

//Java Program: ZigZag Conversion
public class Solution {
    public String convert(String s, int numRows) {
        if (numRows==1) {
            return s;
        }
        char[] r = new char[s.length()];
char[][] c = new char[numRows][(s.length()/(2*numRows-2)+1)*(numRows-1)];
for(int i=0;i<s.length();++i) {
if (i%(2*numRows-2)<numRows) {
c[i%(2*numRows-2)][i/(2*numRows-2)*(numRows-1)] = s.charAt(i);
} else {
c[2*numRows-2-i%(2*numRows-2)][i/(2*numRows-2)*(numRows-1)+i%(2*numRows-2)-numRows+1] = s.charAt(i);
}
}
for(int k=0,i=0;i<c.length;++i) {
for(int j=0;j<c[0].length;++j) {
if (c[i][j]!='\u0000') {
r[k++] = c[i][j]; 
}
}
}
return String.valueOf(r);
    }
}