C code代表异或链表 [英] C code for XOR linked list

问题描述

我一直在努力实现异或链表以及其业务，但我一直没能做正确的。

I have been trying to implement XOR linked list and its operations but I have not been able to do it properly.

是否有可能实现在C，因为XOR链接列表上包括的地址的操作？

Is it possible to implement it in C since XOR link list involves operations on addresses?

如果一些实际工作code给出我将非常感激。

I would be very thankful if some actual working code is given.

推荐答案

这是我以前没有见过一个有趣的想法。随着今天的还算充裕的内存，这似乎是一个很大的复杂性而收效甚微（虽然不是所有平台的内存冲洗）。 修改虽然做我真正的工作，我的脑海里不停地漂流回来吧，所以我增加了函数来创建新的节点，并把它放在指定的结束。现在prettier。这是相当清凉，无论是addnode的和遍历功能是对称的。既不需要知道方向。只要给它列表的一端，他们​​正常工作。

That's an interesting idea that I have not seen before. With today's fairly abundant memory, it seems like a lot of complexity for little gain (although not all platforms are flush with memory). Edit While doing my real work, my mind kept drifting back to it, so I added the function to create the new node and put it on the given end. Prettier now. It's rather cool that both the addnode and traverse functions are symmetrical. Neither needs to know the direction. Just give it one end of the list and they operate correctly.

和基于达隆的评论（感谢），我改变了int值使用intptr_t 便携性。

And based on Darron's comment (thanks), I changed the int to intptr_t for portability.

#include <stdio.h>
#include <malloc.h>
#include <stdint.h>  // gcc needs this for intptr_t.  

typedef struct xorll {
   int  value;
   struct xorll  *np;
}  xorll;


// traverse the list given either the head or the tail
void traverse( xorll *start )  // point to head or tail
{
   xorll *prev, *cur;

   cur = prev = start;
   while ( cur )
      {
      printf( "value = %d\n", cur->value );
      if ( cur->np == cur )
         // done
         break;
      if ( cur == prev )
         cur = cur->np;   // start of list
      else {
         xorll *save = cur;
         cur = (xorll*)((uintptr_t)prev ^ (uintptr_t)cur->np);
         prev = save;
         }
      }
}

// create a new node adding it to the given end and return it
xorll* newnode( xorll *prev, xorll *cur, int value )
{
   xorll *next;

   next = (xorll*)malloc( sizeof( xorll ));
   next->value = value;
   next->np = cur;  // end node points to previous one

   if ( cur == NULL )
      ; // very first node - we'll just return it
   else if ( prev == NULL ) {
      // this is the second node (they point at each other)
      cur->np = next;
      next->np = cur;
      }
   else {
      // do the xor magic
      cur->np = (xorll*)((uintptr_t)prev ^ (uintptr_t)next);
      }

   return next;
}



int main( int argc, char* argv[] )
{
   xorll *head, *tail;
   int   value = 1;

   // the first two nodes point at each other.  Weird param calls to
   // get the list started
   head = tail = newnode( NULL, NULL, value++ );
   tail = newnode( NULL, tail, value++ );

   // now add a couple to the end
   tail = newnode( tail->np, tail, value++ );
   tail = newnode( tail->np, tail, value++ );

   // this is cool - add a new head node
   head = newnode( head->np, head, 999 );


   printf( "Forwards:\n" );
   traverse( head );
   printf( "Backwards:\n" );
   traverse( tail );


}

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