如下程序用于打印字母三角形,请填空。 static void Main(string[] args ) { int i, j, k, n; char x ; Console.Write (" 请输入要打印图形的行数: "); n = int.Parse ( Console.ReadLine ()); for (i = 1; i <= n; i++) { x=____________; for (j = 1; j <= n - i; j++) Console.Write (" "); for (k = 1; k <= 2 * i - 1; k++) Console.Write ("{0}", _____); Console.WriteLine (); } }