用回溯法找出 n 个自然数中取 r 个数的全排列

using System;
using System.Collections.Generic;
using System.Text;
【用回溯法找出 n 个自然数中取 r 个数的全排列】namespace ExArrange
{
class Arrange
{
public void Arrange(int n, int r)
{
int i = 0, j;
string s;
int[] a = new int[n];
a[i] = 1;
while (true)
{
if ((a[i] - i) <= (n - r + 1))
{
if (i == (r - 1))
{
s = "";
for (j = 0; j < r; j++)
{
s = s + Convert.ToString(a[j]) + ",";
}
// Memo1.Lines.Append(Trim(s));
Console.WriteLine(s);
a[i] = a[i] + 1;
continue;
}
i = i + 1;
a[i] = a[i - 1] + 1;
}
else
{
if (i == 0)
{
break;
}
i = i - 1;
a[i] = a[i] + 1;
}
}
}
static void Main(string[] args)
{
Ex03_19 e = new Ex03_19();
e.Arrange(6, 3);
}
}
}

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