单链表（三）

较之（二）差别不大，进修改了函数insertascend(按不降方式插入)insertdown(按不升方式插入)，主要是参考《C与指针》这本书中第十二章 使用结构和指针提供的思路~~

/************************************************************************//* author : thomasE-mail: [e-mail] 2011-5-13 in lab of NJUPT *//************************************************************************/#include <stdio.h>#include <malloc.h>typedef struct tag{int data;struct tag *next;} node, *nodep;node *creat( int num ){nodep p;p = ( nodep )malloc( sizeof( node ) ); p -> data = num;p -> next = NULL;return p;}int length( node *head ){int n = 0;node *p;p = head;while ( p != NULL ){n++;p = p ->next;} return n;}void print( node *head ){node *p;int i = 0;int n = length(head);p = head;if ( p == NULL ){printf("the list is empty! /n");}else{printf("these %d records are : /n", n);for ( i = 1; i <=n; i++){printf("the %d record is: %d /n", i, p -> data );if ( i != n){p = p -> next;}}}}//根据《C与指针》这本书提供的思想进行优化void insertascend( nodep *head, int num ){nodep current;nodep newnode;while ( (current = *head ) != NULL && current -> data < num ){head = ¤t -> next;}newnode = ( nodep )malloc(sizeof(node));newnode -> data = num;newnode -> next = current;*head = newnode;}//void insertdown( nodep *head, int num ){nodep current;nodep newnode;while ( ( current = *head ) != NULL && current -> data > num ){head = ¤t -> next;}newnode = ( nodep )malloc(sizeof(node));newnode -> data = num;newnode -> next = current;*head = newnode;}void del( nodep *head, int num ){nodep current = *head;nodep previous = NULL;while ( current != NULL && current -> data != num ){previous = current;current = current -> next;}if ( current == NULL ){printf("%d not found! /n", num);}else{if ( previous == NULL )*head = current -> next;elseprevious -> next = current -> next;free(current);}}nodep reverse( nodep head ){node *p1, *p2, *p3;if ( head == NULL || head -> next == NULL ){return head;}p1 = head;p2 = head -> next;while ( p2 ){p3 = p2 -> next;p2 -> next = p1;p1 = p2;p2 = p3;}head -> next = NULL;head = p1;return head;}void main(int argc, char *argv[]){nodep head;head = creat(4);print(head);insertdown( &head, 3);//insertascend( &head, 3);print(head);insertdown( &head, 5);//insertascend( &head, 5);print(head);del( &head, 4 );print(head);}