【LeetCode】6. Z 字形变换

public string Convert(string s, int numRows)
{
    if (string.IsNullOrEmpty(s)) return s;

    if (numRows <= 1) return s;

    var offset = 2 * numRows - 2;
    var index = 0;
    var chars = new Char[s.Length];

    for (int i = 0; i < numRows; i++)
    {
        var subOffset = offset - 2 * i;
        for (int k = 0; (i + k) < s.Length; k += offset)
        {
            chars[index++] = s[i + k];

            if (i == 0 || i == numRows - 1) continue;

            if (i + k + subOffset < s.Length) chars[index++] = s[i + k + subOffset];
        }
    }

    return new String(chars);
}