只能获取 fixed 语句初始值设定项内的未固定表达式的地址

[yanglei492064776]

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
// compile with: /unsafe;

namespace myPerm
{
class Program
{
// delegate void ProcessDelegate(int x, int y);

public unsafe static void swap(int *i, int *j)
{

int temp = *i;
*i = *j;
*j = temp;
}

static int n=0 ;
public unsafe static int Perm(int[] a, int k, int m)
{
// ProcessDelegate myDelegate = new ProcessDelegate(swap);
if (k > m)
{

for (int i = 0; i <= m; i++)
{
Console.Write(" " + a[i] + " ");
}
Console.WriteLine();
n++;
}
else
{
for (int i = k; i <= m; i++)
{
swap(&a[k], &a[i]);
Perm(a, k + 1, m);
swap(&a[k], &a[i]);
}
}
return n;
}
static void Main(string[] args)
{
int[] list = new int[] { 1, 2, 3, 4, 5 };

int n = Perm(list, 0, 4);

Console.WriteLine("The total are {0} times", n);
Console.ReadKey();
}
}
}

[骑行大地]

修改如下：

        public unsafe static int Perm(int[] a, int k, int m)
        {
            // ProcessDelegate myDelegate = new ProcessDelegate(swap);
            if (k > m)
            {

                for (int i = 0; i <= m; i++)
                {
                    Console.Write("  " + a[i] + "  ");
                }
                Console.WriteLine();
                n++;
            }
            else
            {
                for (int i = k; i <= m; i++)
                {
                    fixed (int* p1 = &a[k], p2 = &a[i])
                    { 
                        //swap(&a[k], &a[i]);
                        swap(p1, p2);
                    }
                    Perm(a, k + 1, m);
                    fixed (int* p1 = &a[k], p2 = &a[i])
                    {
                        //swap(&a[k], &a[i]);
                        swap(p1, p2);
                    }
                }
            }
            return n;
        } 

其他不变。

[骑行大地]

同样学习。fixed语句主要用来防止系统进行“总动内存管理”时移动或释放被某个指针变量所指向的变量。

[随风秀舞]

如果我想把整个char[] name 数组变换为char*的话，
用fixed(char * ptr = name)却是不行。为什么呀？