把list倒序排列，不申请空间。

#include <stdio.h>
#include <stdlib.h>
#include <iostream>
using namespace std;
typedef struct node{
 int  num;
 node *next;
}node_t;
void reverse_list(node_t **pheadmain);
void print_list(node_t *pheadmain);
void free_list(node_t *pheadmain);
void main()
{
 node_t *phead = NULL;
 node_t *pheadtemp = NULL;
 node_t *temp = NULL;
 int i;
 phead = (node_t *)malloc(sizeof(node_t));
 phead->num = 0;
 phead->next = NULL;
 pheadtemp = phead;
 for(i=1; i<5; i++)
 {
  temp = (node_t *)malloc(sizeof(node_t));
  temp->num = i;
  temp->next = NULL;
  pheadtemp->next = temp;
  pheadtemp = pheadtemp->next;
 }
 print_list(phead);
 reverse_list(&phead);
  print_list(phead);
 free_list(phead);
}
void free_list(node_t *pheadmain)
{
 node_t *phead = pheadmain;
 node_t *pheadtemp = NULL;
 while(phead != NULL)
 {
  pheadtemp = phead->next;
  free(phead);
  phead = pheadtemp;
 }
}

void print_list(node_t *pheadmain)
{
 node_t *phead = pheadmain;
 while(phead != NULL)
 {
  cout<<phead->num<<" ";
  phead = phead->next;
 }
 cout<<endl;
}
void reverse_list(node_t **pheadmain)
{
 node_t *phead = *pheadmain;
 node_t *pheadPPP = NULL;
 node_t *pheadQQQ = NULL;
 
 pheadPPP = phead;
 phead = phead->next;
 pheadPPP->next = NULL;/*init*/
 while(phead != NULL)
 {
  pheadQQQ = phead->next;
  phead->next = pheadPPP;
  pheadPPP = phead;
  phead = pheadQQQ;
 }
 *pheadmain = pheadPPP;
}