双链表的插入

预编译

#include <stdlib.h>
#include <stdio.h>
#define status int
#define TRUE 1
#define FALSE 0

typedef struct NODE{
    int value;            /* 存放结点值 */
    struct NODE *prev;  /* 指向前一个结点 */
    struct NODE *next;  /* 指向下一个结点 */
}Node;

数据结构

 1 /*
 2 功能描述:
 3     插入新结点( 从小到大 )
 4
 5 参数:
 6     rootp -- 指向根结点的双指针
 7     new_value -- 要插入链表的新值
 8
 9 返回值：
10     如果插入成功，返回TRUE；
11     否则，返回FALSE
12 */
13 status
14 Insert( Node **rootp, int new_value )
15 {
16     Node *current = *rootp;
17     Node *_new = NULL;
18
19     /* 寻找插入位置 */
20     while ( current != NULL ){
21         if ( current->value > new_value )
22             break;
23
24         if ( current->value == new_value ){
25             printf( "值%d已存在\n", new_value );
26             return FALSE;
27         }
28         current = current->next;
29     }
30
31     /* 创建新结点 */
32     _new = (Node *)malloc( sizeof( Node ) );
33     if ( _new == NULL ){
34         printf( "内存不够\n" );
35         return FALSE;
36     }
37     _new->value = new_value;
38
39     /* 插入新结点 */
40     if ( current == NULL ){
41         if ( current == *rootp ){    /* 插入到空链表 */
42             *rootp = _new;
43             _new->prev = _new;
44             _new->next = NULL;
45
46         }else{                        /* 插入到尾部 */
47             _new->next = NULL;
48             _new->prev = (*rootp)->prev;
49             (*rootp)->prev->next = _new;
50             (*rootp)->prev = _new;
51         }
52     }else{
53         if ( current == *rootp ){    /* 插入到根结点前 */
54             _new->prev = (*rootp)->prev;
55             _new->next = current;
56             current->prev = _new;
57             *rootp = _new;
58
59         }else{                        /* 插入到中间某个结点前 */
60             _new->prev = current->prev;
61             current->prev->next = _new;
62             _new->next = current;
63             current->prev = _new;
64         }
65     }
66
67     return TRUE;
68 }

插入代码

 1 /*
 2 功能描述:
 3     插入新结点( 从小到大 )
 4
 5 参数:
 6     rootp -- 指向根结点的双指针
 7     new_value -- 要插入链表的新值
 8
 9 返回值：
10     如果插入成功，返回TRUE；
11     否则，返回FALSE
12 */
13 status
14 Insert( Node **rootp, int new_value )
15 {
16     Node *current = *rootp;
17     Node *_new = NULL;
18
19     /* 寻找插入位置 */
20     while ( current != NULL ){
21         if ( current->value > new_value )
22             break;
23
24         if ( current->value == new_value ){
25             printf( "值%d已存在\n", new_value );
26             return FALSE;
27         }
28         current = current->next;
29     }
30
31     /* 创建新结点 */
32     _new = (Node *)malloc( sizeof( Node ) );
33     if ( _new == NULL ){
34         printf( "内存不够\n" );
35         return FALSE;
36     }
37     _new->value = new_value;
38
39     /* 插入新结点 */
40     if ( current == NULL ){            /* 插入根结点或尾结点 */
41         if ( current != *rootp ){
42             (*rootp)->prev->next = _new;
43         }
44         _new->prev = (current == *rootp) ? _new : (*rootp)->prev;
45         _new->next = NULL;
46         ((current == *rootp) ? *rootp : (*rootp)->prev ) = _new;
47
48     }else{                            /* 插入到根结点或中间结点之前 */
49         _new->prev = current->prev;
50         ((current == *rootp) ? current->prev : current->prev->next ) = _new;
51         _new->next = current;
52         ((current == *rootp) ? *rootp : current->prev ) = _new;
53     }
54
55     return TRUE;
56 }

优化后的插入代码