/// <summary>
/// 输出一个数组的全排列
/// </summary>
/// <param name="array"></param>
private static void PrintFullPermutation(int[] array)
{
 //0.合法性校验
 if (array == null || array.Length == 0)
 {
  return;
 }
 //1.复制一个新数组：修改时在临时数组中修改
 int[] temp = new int[array.Length];
 for (int i = 0; i < array.Length; i++)
 {
  temp[i] = array[i];
 }
 //2.将新数组升序排列
 int itemp;
 for (int i = 0; i < temp.Length; i++)
 {
  for (int j = i; j < temp.Length; j++)
  {
   itemp = array[i];
   array[i] = array[j];
   array[j] = itemp;
  }
 }
 //3.依次寻找并打印全排序
 PrintArray(temp);
 while (!isDesc(temp))
 {
  FindNextArray(temp);
  PrintArray(temp);
 }
}
/// <summary>
/// 打印数组
/// </summary>
/// <param name="array">数组</param>
private static void PrintArray(int[] array)
{
 for (int i = 0; i < array.Length; i++)
 {
  Console.Write(array[i].ToString() + '\t');
 }
 Console.WriteLine();
}
/// <summary>
/// 判断一个数组内元素是否降序排列
/// </summary>
/// <param name="array">数组</param>
/// <returns></returns>
private static bool isDesc(int[] array)
{
 int temp=array[0];
 for (int i = 1; i < array.Length; i++)
 {
  if (array[i] > array[i - 1])
  {
   return false;
  }
 }
 return true;
}
/// <summary>
/// 找到下一组排列
/// </summary>
/// <param name="array"></param>
private static void FindNextArray(int[] array)
{
 //1.找出数组的最大值
 int max = array[0];
 for (int i = 1; i < array.Length; i++)
 {
  if (max < array[i])
  {
   max = array[i];
  }
 }
 //2.从后向前找：找到第一组后数大于前数，以后数位置为signer
 int signer = array.Length - 1;
 for (int i = array.Length - 1; i > 0; i--)
 {
  if (array[i] > array[i - 1])
  {
   signer = i;
   break;
  }
 }
 //3.从signer向后找：找到大于且最接近于array[signer-1]的数array[t]
 int t = signer;
 for (int i = signer; i < array.Length; i++)
 {
  if (array[i] > array[signer - 1] && array[i] < max)
  {
   t = i;
   max = array[t];
  }
 }
 //4.将找到的array[t]和array[signer-1]互换
 int temp = array[t];
 array[t] = array[signer - 1];
 array[signer - 1] = temp;
 //5.为signer之后的元素升序排序
 for (int i = signer; i < array.Length; i++)
 {
  for (int j = i + 1; j < array.Length; j++)
  {
   if (array[i] > array[j])
   {
    temp = array[i];
    array[i] = array[j];
    array[j] = temp;
   }
  }
 }
}

static void Main(string[] args)
{
 //求1234四个数字的全排列
 int[] array = new int[] { 1, 2, 3, 4 };
 PrintFullPermutation(array);
 Console.ReadLine();
}