这是一个完整的代码示例，使用函数调用删除匹配的元素：
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rem() 删除匹配的元素，使用 prev
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rem2() 删除匹配元素，使用指针到指针
// code.c
#include <stdio.h>
#include <stdlib.h>
typedef struct list_entry {
int val;
struct list_entry *next;
} list_entry;
list_entry *new_node(list_entry *curr, int val)
{
list_entry *new_n = malloc(sizeof(list_entry));
if (new_n == NULL) {
fputs("Error in malloc\n", stderr);
exit(1);
}
new_n->val = val;
new_n->next = NULL;
if (curr) {
curr->next = new_n;
}
return new_n;
}
#define ARR_LEN(arr) (sizeof(arr)/sizeof((arr)[0]))
#define CREATE_LIST(arr) create_list((arr), ARR_LEN(arr))
list_entry *create_list(const int arr[], size_t len)
{
if (len == 0) {
return NULL;
}
list_entry *node = NULL;
list_entry *head = node = new_node(node, arr[0]);
for (size_t i = 1; i < len; ++i) {
node = new_node(node, arr[i]);
}
return head;
}
void rem(list_entry **head_p, int match_val)
// remove and free all entries with match_val
{
list_entry *prev = NULL;
for (list_entry *entry = *head_p; entry; ) {
if (entry->val == match_val) {
list_entry *del_entry = entry;
entry = entry->next;
if (prev) {
prev->next = entry;
} else {
*head_p = entry;
}
free(del_entry);
} else {
prev = entry;
entry = entry->next;
}
}
}
void rem2(list_entry **pp, int match_val)
// remove and free all entries with match_val
{
list_entry *entry;
while ((entry = *pp)) { // assignment, not equality
if (entry->val == match_val) {
*pp = entry->next;
free(entry);
} else {
pp = &entry->next;
}
}
}
void print_and_free_list(list_entry *entry)
{
list_entry *node;
// iterate through, printing entries, and then freeing them
for (; entry != NULL; node = entry, /* lag behind to free */
entry = entry->next,
free(node)) {
printf("%d ", entry->val);
}
putchar('\n');
}
#define CREATELIST_REMOVEMATCHELEMS_PRINT(arr, match_val) createList_removeMatchElems_print((arr), ARR_LEN(arr), (match_val))
void createList_removeMatchElems_print(const int arr[], size_t len, int match_val)
{
list_entry *head = create_list(arr, len);
rem2(&head, match_val);
print_and_free_list(head);
}
int main()
{
const int match_val = 2; // the value to remove
{
const int arr[] = {0, 1, 2, 3};
CREATELIST_REMOVEMATCHELEMS_PRINT(arr, match_val);
}
{
const int arr[] = {0, 2, 2, 3};
CREATELIST_REMOVEMATCHELEMS_PRINT(arr, match_val);
}
{
const int arr[] = {2, 7, 8, 2};
CREATELIST_REMOVEMATCHELEMS_PRINT(arr, match_val);
}
{
const int arr[] = {2, 2, 3, 3};
CREATELIST_REMOVEMATCHELEMS_PRINT(arr, match_val);
}
{
const int arr[] = {0, 0, 2, 2};
CREATELIST_REMOVEMATCHELEMS_PRINT(arr, match_val);
}
{
const int arr[] = {2, 2, 2, 2};
CREATELIST_REMOVEMATCHELEMS_PRINT(arr, match_val);
}
{
const int arr[] = {};
CREATELIST_REMOVEMATCHELEMS_PRINT(arr, match_val);
}
return 0;
}
在此处查看实际代码：
如果像这样编译和使用 valgrind（内存泄漏检查器）：
gcc -std=c11 -Wall -Wextra -Werror -o go code.c && valgrind ./go
我们看到一切都很好。