C字典和JSON是兩種非常常用的數據結構，它們都可以存儲鍵值對，用于在程序中處理和傳輸數據。下面我們來具體了解一下它們的特點和使用。

一、C字典

C字典是一種哈希表結構，使用鍵值對來存儲數據，可以快速地查找和讀取數據。具體使用方法如下：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define HASH_SIZE 997
typedef struct hash_entry {
char *key;
char *value;
struct hash_entry *next;
} hash_entry;
typedef struct hash_table {
hash_entry **table;
} hash_table;
hash_table *hash_create() {
hash_table *t = (hash_table *)malloc(sizeof(hash_table));
t->table = (hash_entry **)calloc(HASH_SIZE, sizeof(hash_entry *));
return t;
}
void hash_destroy(hash_table *t) {
int i;
for (i = 0; i< HASH_SIZE; i++) {
hash_entry *e, *prev = NULL;
e = t->table[i];
while (e) {
prev = e;
e = e->next;
free(prev->key);
free(prev->value);
free(prev);
}
}
free(t->table);
free(t);
}
int hash_func(char *key) {
int h = 0;
while (*key) {
h = (h<< 4) + *key++;
unsigned int g = h & 0xf0000000;
if (g != 0) {
h ^= g >>24;
h &= ~g;
}
}
return h % HASH_SIZE;
}
void hash_set(hash_table *t, char *key, char *value) {
int h = hash_func(key);
hash_entry *e, *next;
for (e = t->table[h]; e != NULL; e = next) {
next = e->next;
if (strcmp(e->key, key) == 0) {
free(e->value);
e->value = strdup(value);
return;
}
}
e = (hash_entry *)malloc(sizeof(hash_entry));
e->key = strdup(key);
e->value = strdup(value);
e->next = t->table[h];
t->table[h] = e;
}
char *hash_get(hash_table *t, char *key) {
int h = hash_func(key);
hash_entry *e;
for (e = t->table[h]; e != NULL; e = e->next) {
if (strcmp(e->key, key) == 0) {
return e->value;
}
}
return NULL;
}
int main(int argc, char **argv) {
hash_table *t = hash_create();
hash_set(t, "key1", "value1");
hash_set(t, "key2", "value2");
hash_set(t, "key3", "value3");
printf("%s\n", hash_get(t, "key1"));
printf("%s\n", hash_get(t, "key2"));
printf("%s\n", hash_get(t, "key3"));
hash_destroy(t);
return 0;
}

二、JSON

JSON是一種輕量級的數據交換格式，具有易讀性和易于解析的特點。JSON可以表示數組、對象、字符串、數字、布爾值和null值。具體使用方法如下：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <jansson.h>
int main(int argc, char **argv) {
json_t *json = json_object();
json_object_set_new(json, "key1", json_integer(1));
json_object_set_new(json, "key2", json_real(2.0));
json_object_set_new(json, "key3", json_true());
char *json_str = json_dumps(json, JSON_INDENT(2));
printf("%s\n", json_str);
json_decref(json);
free(json_str);
return 0;
}

以上就是C字典和JSON的基本介紹和使用方法，希望對讀者們有所幫助。