C算法-UT哈希

汇总：
参考：http://troydhanson.github.io/uthash/userguide.html

一、键值是INT型
1、定义结构体，对应键值是整形int，需要有个全局指针比如users

typedef struct  {
    
    
	int id;                    /* key */
	char name[10];
	int cnt;
	UT_hash_handle hh;         /* makes this structure hashable */
}my_struct;
my_struct *users = NULL;    /* important! initialize to NULL */

2、ADD&查找操作
先HASH_FIND_INT，如果不能找到，那么新加到HASH_ADD_INT中；如果能找到，就对cnt++；
注意HASH_FIND_INT的第二个入参是当前键值的名称

void add_user(int user_id, char *name, int cnt) {
    
    
	my_struct *s;
	HASH_FIND_INT(users, &user_id, s);  /* id already in the hash? */
	if (s == NULL) {
    
    
		s = (my_struct *)malloc(sizeof *s);
		s->id = user_id;
		s->cnt = cnt;
		strcpy(s->name, name);
		HASH_ADD_INT(users, id, s);  /* id: name of key field */
	} else {
    
    
		s->cnt += cnt;
	}
}

3、这个遍历操作比较新鲜；next是s->hh.next

void print_users() {
    
    
	my_struct *s;
	for (s = users; s != NULL; s = s->hh.next) {
    
    
		printf("user id %d: name %s cnt %d\n", s->id, s->name, s->cnt);
	}
}

4、排序操作

int id_sort(my_struct *a, my_struct *b) {
    
    
	return (a->id - b->id);
}

void sort_by_id() {
    
    
	HASH_SORT(users, id_sort);
}

5、计数操作

	unsigned int num_users;
	num_users = HASH_COUNT(users);
	printf("\nthere are %u users\n", num_users)

6、删除操作

void delete_all() {
    
    
	my_struct *current_user, *tmp;

	HASH_ITER(hh, users, current_user, tmp) {
    
    
		HASH_DEL(users, current_user);  /* delete; users advances to next */
		free(current_user);            /* optional- if you want to free  */
	}
}

Main结果

int main(){
    
    	
	add_user(2002, "zhao", 10);
	add_user(1003, "qian", 5);
	add_user(1003, "qian", 2);
	add_user(2002, "zhao", 3);
	add_user(3001, "li", 9);
	print_users();

	sort_by_id();
	printf("\nafter sort:\n");
	print_users();

	unsigned int num_users;
	num_users = HASH_COUNT(users);
	printf("\nthere are %u users\n", num_users);

	delete_all();
	return 0;
}

二、键值是string型

typedef struct {
    
    
	int id;                    
	char name[10];				/* key */
	int cnt;
	UT_hash_handle hh;         /* makes this structure hashable */
}my_struct;
my_struct *users = NULL;    /* important! initialize to NULL */
void add_user(int user_id, char *name, int cnt) {
    
    
	my_struct *s;
	HASH_FIND_STR(users, name, s);  /* id already in the hash? */
	if (s == NULL) {
    
    
		s = (my_struct *)malloc(sizeof *s);
		s->id = user_id;
		s->cnt = cnt;
		strcpy(s->name, name);
		HASH_ADD_STR(users, name, s);  /* id: name of key field */
	}
	else {
    
    
		s->cnt += cnt;
	}
}

main函数

三、键值是String指针型

typedef struct {
    
    
	int id;
	char *name;				/* key */
	int cnt;
	UT_hash_handle hh;         /* makes this structure hashable */
}my_struct;
my_struct *users = NULL;    /* important! initialize to NULL */
void add_user(int user_id, char *name, int cnt) {
    
    
	my_struct *s;
	HASH_FIND_STR(users, name, s);  /* id already in the hash? */
	if (s == NULL) {
    
    
		s = (my_struct *)malloc(sizeof *s);
		s->id = user_id;
		s->cnt = cnt;
		s->name = name;
		HASH_ADD_KEYPTR(hh, users, s->name, strlen(s->name), s);  /* id: name of key field */
	}
	else {
    
    
		s->cnt += cnt;
	}
}

四、键值是结构体

typedef struct {
    
    
	char *name;
	int id;
}Person;

typedef struct {
    
    
	Person per;				/* key */
	int cnt;
	UT_hash_handle hh;         /* makes this structure hashable */
}my_struct;
my_struct *users = NULL;    /* important! initialize to NULL */
void add_user(int user_id, char *name, int cnt) {
    
    
	my_struct *s = NULL;
	Person input;
	input.name = name;
	input.id = user_id;
	HASH_FIND(hh, users, &input, sizeof(Person), s);  /* id already in the hash? */
	if (s == NULL) {
    
    
		s = (my_struct *)malloc(sizeof *s);
		s->per.id = user_id;
		s->cnt = cnt;
		s->per.name = name;
		HASH_ADD(hh, users, per, sizeof(Person), s);
	}
	else {
    
    
		s->cnt += cnt;
	}
}