合并有序链表

最新推荐文章于 2025-05-07 08:00:00 发布

原创最新推荐文章于 2025-05-07 08:00:00 发布 · 111 阅读

CC 4.0 BY-SA版权

本文介绍了一种将两个已排序的链表合并成一个有序链表的算法，并提供了三种不同的实现方式，包括直接迭代、宏定义辅助迭代及使用lambda表达式进行迭代。

///方法一
inline void iter_next(node* &pn)
{
  pn = pn->next;
}

void merge_order_list(node* phead1, node* phead2, node* &phead)
{
  if(NULL == phead1) { phead = phead2;  return;}
  if(NULL == phead2) { phead = phead1;  return;}

  node *pthead, *pmin;
  pthead = phead1->value < phead2->value? phead1: phead2;
  phead  = pthead;
  
  while (phead1 && phead2) {
    pmin = phead1->value < phead2->value ? phead1 : phead2;
    if(pthead->value != pmin->value) {
      pthead->next = pmin;
      iter_next(pthead);
    }          

    if(phead1->value < phead2->value) iter_next(phead1);
    else if(phead1->value > phead2->value) iter_next(phead2);
    else {
      iter_next(phead1);
      iter_next(phead2);
    }
  }

  phead1 = (NULL == phead1) ? phead2 : phead1;
  while(phead1) {
    pthead->next = phead1;
    iter_next(pthead);
    iter_next(phead1);
  }

  pthead->next = NULL;
}


///方法二
#define ITER_NEXT(pn) \
do { \
  pn = (pn)->next;\
} while(0)

#define NEXT(phead1, phead2, pthead) \
do {\
    if((pthead)->value != (phead1)->value) {\
      (pthead)->next = (phead1);\
      ITER_NEXT(pthead);\
    } \
    ITER_NEXT(phead1);\
    if((phead1)->value == (phead2)->value) ITER_NEXT(phead2);\
}while(0)

void merge_order_list(node* phead1, node* phead2, node* &phead)
{
  if(NULL == phead1) { phead = phead2;  return;}
  if(NULL == phead2) { phead = phead1;  return;}

  node *pthead = (phead1->value < phead2->value)? phead1: phead2;
  phead  = pthead;
  while(phead1 && phead2) {
    if(phead1->value < phead2->value)  NEXT(phead1,phead2,pthead);
    else NEXT(phead2, phead1,pthead);
  }

  phead1 = (NULL == phead1) ? phead2 : phead1;
  while(phead1) {
    pthead->next = phead1;
    ITER_NEXT(pthead);
    ITER_NEXT(phead1);
  }

  pthead->next = NULL;
}


//方法三
void merge_order_list(node* phead1, node* phead2, node* &phead)
{
    if(NULL == phead1) { phead = phead2;  return;}
    if(NULL == phead2) { phead = phead1;  return;}

    node *pthead = (phead1->value < phead2->value)? phead1: phead2;
    phead  = pthead;

    auto f = [&pthead](node* &phead1,node* &phead2) {
        if(pthead->value != phead1->value) {
            pthead->next = phead1;
            ITER_NEXT(pthead);
        }   
        ITER_NEXT(phead1);
        if(phead1->value == phead2->value) ITER_NEXT(phead2);
    };  

    while(phead1 && phead2) {
        if(phead1->value < phead2->value)  f(phead1,phead2);
        else f(phead2, phead1);
    }

    phead1 = (NULL == phead1) ? phead2 : phead1;
    while(phead1) {
        pthead->next = phead1;
        ITER_NEXT(pthead);
        ITER_NEXT(phead1);
    }

    pthead->next = NULL;
}