双向链表（一）

本人写的双向链表，基本函数功能和单链表一致，未优化版，只是实现不一样~~欢迎批评指正

/************************************************************************/ /* author : thomas E-mail: chenhua308@gmail.com */ /************************************************************************/ #include <stdio.h> #include <malloc.h> typedef struct tag { int data; struct tag *next; struct tag *pre; } dnode; //create bi-list dnode *creat( int i ) { dnode *head; head = (dnode *)malloc(sizeof(dnode)); head -> next = NULL; head -> pre = NULL; head -> data = i; return head; } //compute the length of bi-list int length( dnode *head ) { int n = 0; dnode *p; p = head; while ( p != NULL ) { n++; p = p -> next; } return n; } //print bi-list void printnext( dnode *head ) { dnode *p; int n = length( head ); int i ; printf("/n these %d records are : /n", n); p = head; for ( i = 1; i <=n; i++) { printf("the %d record is: %d /n", i, p -> data ); if ( i != n) { p = p -> next; } } } void printprev( dnode *head ) { dnode *p; int n = length( head ); int i; printf("/n these %d records are : /n", n); p = head; while ( p -> next != NULL ) p = p -> next; for ( i = 1; i <=n; i++) { printf("the %d record is: %d /n", i, p -> data ); if ( i != n) { p = p -> pre; } } } //insert in the direction of ascend dnode *insertascend( dnode *head, int num ) { dnode *p0, *p1, *p2; p0 = ( dnode * )malloc( sizeof(dnode) ); p0 -> data = num; p1 = head; while ( p1 -> next != NULL && p1 -> data < p0 -> data) { p2 = p1; p1 = p1 -> next; } if ( p1 == head ) { if ( p1 -> data >= p0 -> data ) { p0 -> pre = NULL; p0 -> next = p1; p1 -> pre = p0; head = p0; } else { p0 -> next = NULL; p0 -> pre = p1; p1 -> next = p0; } } else if ( p1 -> next == NULL ) { if ( p1 -> data >= p0 -> data ) { p0 -> next = p1; p1 -> pre = p2; p2 -> next = p0; } else { p0 -> next = NULL; p0 -> pre = p1; p1 -> next = p0; } } else { p0 -> next = p1; p0 -> pre = p2; p2 -> next = p0; } return head; } dnode *insertdown(dnode *head, int num) { dnode *p0, *p1, *p2; p0 = (dnode *)malloc(sizeof(dnode)); p0 -> data = num; p1 = head; while ( p1 -> next != NULL && p1 -> data > p0 -> data ) { p2 = p1; p1 = p1 -> next; } if ( p1 == head ) { if ( p1 -> data <= p0 -> data ) { p0 -> next = p1; p0 -> pre = NULL; p1 -> pre = p0; head = p0; } else { p1 -> next = p0; p0 -> next = NULL; p0 -> pre = p1; } } else if ( p1 -> next == NULL ) { if ( p1 -> data <= p0 -> data ) { p0 -> next = p1; p0 -> pre = p2; p2 -> next = p0; } else { p1 -> next = p0; p0 -> next = NULL; p0 -> pre = p1; } } else { p0 -> next = p1; p0 -> pre = p2; p2 -> next = p0; } return head; } //delete node dnode *del( dnode *head, int num ) { dnode *p1, *p2; p1 = head; while ( p1 -> next != NULL && num != p1 -> data ) { p2 = p1; p1 = p1 -> next; } if ( num == p1 -> data ) { if ( p1 == head ) { head = p1 -> next; free(p1); } /*else if ( p1 -> next == NULL ) { p2 -> next = NULL; free(p1); }*/ else { p2 -> next = p1 -> next; p1 -> pre = p2; free(p1); } } else { printf("/n %d could not be found", num); } return head; } void main(int argc, char *argv[]) { dnode *head; head = creat(4); printnext(head); printprev(head); //head = insertascend(head, 5); head = insertdown(head, 5); printnext(head); printprev(head); //head = insertascend(head, 2); head = insertdown(head, 2); printnext(head); printprev(head); head = del(head, 5); printnext(head); printprev(head); head = del(head, 3); printnext(head); printprev(head); }