一个面试c程序

燕子的很好。。我一直掉线啊。。。
#include<stdio.h>
#include<malloc.h>
typedef struct node_t
{
    int a;
    struct node_t *next;
}node_t;
node_t * ChangeTwoNodes(node_t *list)
{
    if(list==NULL) return NULL;
    if(list->next==NULL) return list;
    node_t *pret=list->next,*p, *t;    
    for (t=list; (list) && (p=list->next); list=list->next)
    {
        t->next = p;
        list->next = p->next;
        p->next = t = list;
    }
    return pret;
}
node_t * makenode(node_t *list,int n,int i)
{
    list=(node_t *)malloc(sizeof(node_t ));
    list->a=n;
    list->next=NULL;
    if(n==i)
        return list;
    else
    {
        list->next=makenode(list->next,++n, i);
        return list;
    }
}
int main()
{
  node_t *list,*p;
  list=makenode(list,1,6);
  for(p=list;p;p=p->next)
      printf("%d ",p->a);
  printf("\n");
  p=ChangeTwoNodes(list);
  for(;p;p=p->next)
      printf("%d ",p->a);
  printf("\n");
  return 0;
}
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