C++数据结构之链表的创建

// test_shared.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <memory>
#include <string>
#include <iostream>

typedef struct stage_tag {
  int         data_ready;   /* Data present */
  long        data;      /* Data to process */
  struct stage_tag  *next;     /* Next stage */
} stage_t;

// 高效率的链表创建方式
stage_t* TestLinkCreateClever(int stages)
{
  stage_t *head = NULL,*new_stage = NULL,*tail = NULL;
  stage_t **link = &head; // 区别在这个指针地址变量上,它起到绑定新的stage的作用.
  for(int i =0; i<stages;++i)
  {
    new_stage = (stage_t*)malloc(sizeof(stage_t));   
    new_stage->data_ready = 0;
    new_stage->data = i;

    *link = new_stage; // 把新的stage赋值给link指向的指针地址
    link = &new_stage->next; // 绑定下一个的指针地址
  }

  tail = new_stage;
  *link = NULL;

  return head;
}

// 低效率的链表创建方式
stage_t* TestLinkCreateStupid(int stages)
{
  stage_t *head = NULL,*new_stage = NULL,*tail = NULL;
  for(int i =0; i<stages;++i)
  {
    new_stage = (stage_t*)malloc(sizeof(stage_t));   
    new_stage->data_ready = 0;
    new_stage->data = i;
    new_stage->next = NULL;

    if(tail)
      tail->next = new_stage;
    else
      head = new_stage;

    tail = new_stage;
  }
  return head;
}

int _tmain(int argc, _TCHAR* argv[])
{
  std::cout << "=== TestLinkCreateClever ===" << std::endl;
  auto first = TestLinkCreateClever(10);
  while(first)
  {
    std::cout << "data: " << first->data << std::endl;
    first = first->next;
  }

  std::cout << "=== TestLinkCreateStupid ===" << std::endl;
  auto second = TestLinkCreateStupid(10);
  while(second)
  {
    std::cout << "data: " << second->data << std::endl;
    second = second->next;
  }
  return 0;
}