求入栈顺序为1234……N的序列的所有可能的出栈序列

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class Program
{
private static void Fun(int x, int n, Stack stack, List outList,ref int count)
{
if (outList.Count == n)
{
count++;
Console.WriteLine(string.Join(',', outList));
}

if (x <= n)
{
stack.Push(x);
Fun(x + 1, n, stack, outList, ref count);
stack.Pop();
}

if(stack.Count > 0)
{
var temp = stack.Peek();

stack.Pop();
outList.Add(temp);

Fun(x, n, stack, outList, ref count);

stack.Push(temp);
outList.RemoveAt(outList.Count - 1);
}
}

static void Main(string[] args)
{
int n;
string nStr;
while (true)
{
while (true)
{
Console.WriteLine("输入一个正整数：");
nStr = Console.ReadLine();
if (int.TryParse(nStr, out n))
{
break;
}
}

var stack = new Stack();
var outList = new List();
int count = 0;
Fun(1, n, stack, outList, ref count);
Console.WriteLine($"总计{count}种出栈方式。");
}
}
}