链表的基本操作

 

#include  < stdlib.h >
#include  < stdio.h >

typedef  struct  node 
{
     int  data;
     struct  node  * next;
}NODE;

NODE  * head = NULL;

/* 函数声明 */
NODE  * createlist_head( int  len);
NODE  * createlist_end( int  len);
NODE  * createlist_sort( int  len);
int  insert(NODE  * newNode, int  index);
void  insert_sort(NODE  * newNode);
void  display(NODE  * p);

/* 创建新节点 */
NODE  * createNewNode()
{
    NODE  * p;
     int  c;
    scanf( " %d " , & c);
    p = (NODE  * )malloc( sizeof (NODE));
    p -> data = c;
    p -> next = NULL;
     return  p;
}

/* 链表头部插入 */
NODE  * createlist_head( int  len)
{
    NODE  * p;
     int  i,c;
     for  (i = 0 ;i < len;i ++ )
    {
        p = createNewNode();
        p -> next = head;
        head = p;
    }
     return  head;
}

/* 链表尾部插入 */
NODE  * createlist_end( int  len)
{
    NODE  * p, * tail = head;
     int  c,i;
     for  (i = 0 ;i < len;i ++ )
    {
        p = createNewNode();
         if (head == NULL)
            head = p;
         else
            tail -> next = p;
        tail = p;
    }
     return  head;
}

/* 按data成员值大小排序插入 */
NODE  * createlist_sort( int  len)
{
    NODE  * p;
     int  c,i;
     for  (i = 0 ;i < len;i ++ )
    {
        p = createNewNode();
        insert_sort(p);
    }
     return  head;
}

/* 按指定位置进行插入 */
int  insert(NODE  * newNode, int  index)        
{
     int  i = 0 ;
    NODE  * p;
    p = head;
     while  (p != NULL && i < index - 1 )
    {
        p = p -> next;
        i ++ ;
    }
     if (p == NULL)
         return   0 ;
     else
    {
        newNode -> next = p -> next;
        p -> next = newNode;
         return   1 ;
    }
}

/* 按data成员值的大小排序插入 */
void  insert_sort(NODE  * newNode)            
{
    NODE  * p1, * p2;                         // p1,p2记录指标指针位置，一前一后
    p1 = p2 = head;
     while  (p1 != NULL)
    {
         if  (p1 -> data < newNode -> data)         // 成员值比较
        {
            p2 = p1;
            p1 = p1 -> next;
        }
         else
             break ;
    }
     /* 以下代码处理新节点插入位置的各种情况 */

     if (head == NULL)                         // 如果头结点为空，即链表空
        head = newNode;
     else   if (p1 == NULL)                     // 如果到达链表尾部
        p2 -> next = newNode;
     else   if (p1 == head)                     // 如果p1指向头结点
    {
        newNode -> next = p1;
        head = newNode;
    }
     else                                  // 如果p1指向中间节点
    {
        newNode -> next = p1;
        p2 -> next = newNode;
    }
}

/* 显示链表内容 */
void  display(NODE  * p)
{
    NODE  * q;
    q = p;
     while (q != NULL)
    {
        printf( " %d\n " ,q -> data);
        q = q -> next;
    }
    
//      while (p!=NULL)
//      {
//          q=p;
//          p=p->next;
//          free(q);
//      }
}

NODE  * del( int  index)
{
    NODE  * p, * q;
     int  i = 0 ;
    p = head;
     while  (p -> next != NULL && i < index - 1 )
    {
        p = p -> next;
        i ++ ;
    }
     if (p -> next == NULL)
         return  NULL;
     else
    {
        q = p -> next;
        p -> next = q -> next;
         return  q;
    }
}

NODE  * search( char  value)
{
    NODE  * p;
    p = head;
     while (p != NULL && p -> data != value)
        p = p -> next;
     return  p;
}

void  main()
{
     int  flag;
    NODE  * p;
//      display(createlist_sort(5));
//      display(createlist_head(5));
     display(createlist_end( 5 ));
    p = createNewNode();
    flag = insert(p, 3 );
     if (flag)
        printf( " 插入成功！\n " );
     else
        printf( " 插入失败！\n " );
    display(head);
    free(del( 3 ));
    display(head);
}