11#include <stdio.h>
2+ #include <stdlib.h>
3+
4+ /****************************************
5+
6+ 没有头节点，有头指针->首元节点
7+
8+ ****************************************/
29
310typedef struct _drlink_data {
411 char data ;
@@ -14,22 +21,99 @@ static void drlink_show(drlink_data *drldata)
1421 return ;
1522 }
1623
17- for (; ) {
18-
24+ do {
25+ printf ("%c<->" , drlp -> data );
26+ drlp = drlp -> next ;
27+ }while (drlp != drldata );
28+ printf ("//" ); // 双向循环链表 输出时检测正序和逆序是否都正确
29+ drlp = drldata ;
30+ do {
31+ printf ("%c<->" , drlp -> data );
32+ drlp = drlp -> prev ;
33+ }while (drlp != drldata );
34+ printf ("\n" );
35+ }
36+
37+ static void drlink_init (drlink_data * * drldata )
38+ {
39+ * drldata = (drlink_data * )malloc (sizeof (drlink_data ));
40+ if (!drldata ) {
41+ printf ("drldata malloc failed\n" );
42+ return ;
43+ }
44+
45+ (* drldata )-> prev = * drldata ;
46+ (* drldata )-> next = * drldata ;
47+ }
48+
49+ static void drlink_insert (drlink_data * * drldata , unsigned int loc , char data )
50+ {
51+ int i = 0 ;
52+ static int first_init = 1 ;
53+ drlink_data * drlp = * drldata ;
54+ if (!drlp ) {
55+ printf ("drlink is not exsit\n" );
56+ return ;
57+ }
58+
59+ if (first_init == 1 && loc == 0 ) { //第一次insert可以看作是amend了首元节点
60+ (* drldata )-> data = data ;
61+ first_init = 0 ;
62+ return ;
1963 }
2064
65+ drlink_data * ndrldata = (drlink_data * )malloc (sizeof (drlink_data ));
66+ if (!ndrldata ) {
67+ printf ("ndrldata malloc failed\n" );
68+ return ;
69+ }
70+ ndrldata -> data = data ;
71+
72+ if (loc == 0 ) {
73+ drlink_data * pdrldata = drlp -> prev ;
74+ pdrldata -> next = ndrldata ;
75+ ndrldata -> prev = pdrldata ;
76+ ndrldata -> next = drlp ;
77+ drlp -> prev = ndrldata ;
78+ (* drldata ) = ndrldata ;
79+ return ;
80+ }
81+
82+ for (; i < loc ; i ++ ) {
83+ drlp = drlp -> next ;
84+ if (drlp == * drldata ) {
85+ printf ("insert loc %d is invalid\n" , loc );
86+ return ;
87+ }
88+ }
89+ drlink_data * temp = drlp -> prev ;
90+ ndrldata -> next = drlp ;
91+ drlp -> prev = ndrldata ;
92+ temp -> next = ndrldata ;
93+ ndrldata -> prev = temp ;
2194}
2295
2396int main ()
2497{
2598 drlink_data * drldata ;
2699 drlink_show (drldata );
27- #if 0
100+
28101 drlink_init (& drldata );
29- drlink_insert (drldata , 0 , 'a' );
102+ drlink_show (drldata );
103+
104+ drlink_insert (& drldata , 0 , 'a' );
105+ drlink_show (drldata );
106+ drlink_insert (& drldata , 0 , 'a' );
107+ drlink_show (drldata );
108+ drlink_insert (& drldata , 1 , 'e' );
109+ drlink_show (drldata );
110+ drlink_insert (& drldata , 4 , 'i' );
111+ drlink_show (drldata );
112+ #if 0
30113 drlink_delete ();
31114 drlink_amend ();
32115 drlink_select ();
116+ drlink_destroy ();
33117#endif
34118
35119 return 0 ;
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