LeetCode 6 ZigZag Conversion

public class Solution {
	public String convert(String s, int nRows) {
		if (nRows == 1 || s.length() == 0)
			return s;
		boolean flag = false;// 标记生产字符的方向

		StringBuffer[] sb = new StringBuffer[nRows];
		for (int i = 0; i < nRows; i++)
			sb[i] = new StringBuffer("");

		for (int i = 0, j = 0; i < s.length(); i++) {
			sb[j].append(s.charAt(i));
			if (j == nRows - 1)
				flag = true;
			else if (j == 0)
				flag = false;
			if (!flag)
				j++;
			else
				j--;
		}

		for (int i = 1; i < nRows; i++)
			sb[0].append(sb[i]);

		return sb[0].toString();
	}
}