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 s, int numRows);

Example 1:

Input: s = "PAYPALISHIRING", numRows = 3
Output: "PAHNAPLSIIGYIR"

Example 2:

Input: s = "PAYPALISHIRING", numRows = 4
Output: "PINALSIGYAHRPI"
Explanation:

P     I    N
A   L S  I G
Y A   H R
P     I

class Solution {
    public String convert(String s, int row) {
        if (row == 1)
            return s;
        StringBuilder ans = new StringBuilder();
        int chainLength = 2 * (row - 1);
        for (int i = 0; i < row; i++) {
            if (i == 0 || i == row - 1) {
                int temp = i;
                while (temp < s.length()) {
                    ans.append(s.charAt(temp));
                    temp += chainLength;
                }
            } else {
                int temp = i;
                int distanceFromLowerEdge = (row - 1) - i;
                while (temp < s.length()) {
                    ans.append(s.charAt(temp));
                    if (temp + 2 * distanceFromLowerEdge < s.length())
                        ans.append(s.charAt(temp + 2 * distanceFromLowerEdge));
                    temp += chainLength;
                }
            }
        }
        return ans.toString();
    }
}