따라 배우는 C언어 : 15

🙇‍♀️15

🪐구조체

struct Patient
{
    char name[MAX_NAME];
    float height;
    float weight;
    int age;
}

struct Patient p1, p2, p3;

strcpy(p1.name, "seo");
p1.height = 174.0f;
p1.weight = 72.5f;
p1.age = 24;

🪐구조체의 기본적인 사용법

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX 41

struct Person /* Person is a tag of strcutre*/
{
	char name[MAX]; // member
	int age; // member
	float height; // member
};

int main()
{
	int flag; // Receives return value of scanf()

	/* Structre variable */

	struct Person genie;

	/* sot(.) is structure membership operator (member access operator, member operator) */

	strcpy(genie.name, "Will Smith");
	//strncpy(genie.name, "Will Smith", MAX);

	genie.age = 1000;

	// dot(.) has higher precedence than &
	flag = scanf("%f", &genie.height); // &(genie.height)
	printf("%f\n", genie.height);

	/* Initialization */

	struct Person princess = { "Naomi Scott", 18, 160.0f };

	struct Person princess2 = {
		"Naomi Scott",
		18,
		160.0f
	};

	strcpy(princess.name, "Naomi Scott");
	princess.age = 18;
	princess.height = 160.0f;

	/* Designated initailizers */

	struct Person beauty = {
		.age = 18,
		.name = "Bell",
		.height = 150.0f
	};

	//struct Person beauty = { .age = 19, .name = "Bell",.height = 150.0f };

	/* Pointer to a structure variable */

	struct Person* someone;

	someone = &genie;
	//someone = (struct Person*)malloc(sizeof(struct Person)); // and free late

	/* Indirect member(ship) operator (or structure pointer operator) */

	someone->age = 1001; // arrow(->) operator
	printf("%s %s\n", someone->name, (*someone).age);

	/* Structure declarations in a function */

	struct Book
	{
		char title[MAX];
		float price;
	};

	/* No tag */

	struct {
		char farm[MAX];
		float price;
	} apple, apple2;

	strcpy(apple.farm, "Trade Joe");
	apple.price = 1.2f;

	strcpy(apple2.farm, "Safeway");
	apple2.price = 5.6f;

	/* typedef and structure */

	typedef struct Person my_person;
	
	my_person p3;

	typedef struct Person person;

	person p4;

	typedef struct {
		char name[MAX];
		char hobby[MAX];
	} friend;

	friend f4;

	return 0;
}

🪐구조체의 배열 연습문제

#include <stdio.h>
#include <string.h>

#define MAX_TITLE 40
#define MAX_AUTHOR 40
#define MAX_BOOKS 3 /* maximum number of books */

char* s_gets(char* st, int n)
{
	char* ret_val;
	char* find;

	ret_val = fgets(st, n, stdin); // vs. scanf()
	if (ret_val)
	{
		find = strchr(st, '\n');	// look for newline
		if (find)					// if the address is not NULL
			*find = '\0';			// place a null character there
		else
			while (getchar() != '\n')
				continue;			// dispose of rest of line
	}

	return ret_val;
}

struct book
{
	char title[MAX_TITLE];
	char author[MAX_AUTHOR];
	float price;
};

int main()
{
	struct book library[MAX_BOOKS] = { {"Empty", "Empty", 0.0f}, }; /* array of book structures */

	int count = 0;

	while (1)
	{
		printf("Input a book title or press [Enter] to stop.\n>>");
		// TODO: input title
		if (s_gets(library[count].title, MAX_TITLE) == NULL) break;;
		// TODO: break if the first character of the input title is '\0'
		if (library[count].title[0] == '\0') break;

		printf("Input the author.\n>>");
		// TODO: input author name
		s_gets(library->author, MAX_AUTHOR);

		printf("Input the price.\n>>");
		// TODO: input price
		int flag = scanf("%f", &library[count].price);
		// TODO: clear buffer
		while (getchar() != '\n')
			continue;	/* clear input line */

		count++;

		if (count == MAX_BOOKS)
		{
			printf("No more books.\n");
			break;
		}
	}
	if (count > 0)
	{
		printf("\nThe list of books.\n");
		for (int index = 0; index < count; index++)
			printf("\"%s\" written by %s: $%.1f\n",
				library[index].title, library[index].author, library[index].price);
	}
	else
		printf("No books to show.\n");

	return 0;
}

🪐구조체와 함수 연습문제

#include <stdio.h>
#include <string.h>

#define NLEN 20

// 구조체와 함수 연습문제
// 나의 이름을 입력 받고 character수 와 함께 이름 출력

struct name_count
{
	char first[NLEN]; // first name
	char last[NLEN]; // last name
	int num;
};

void receive_input(struct name_count*);
void count_characters(struct name_count*);
void show_result(const struct name_count*);
char* s_gets(char* st, int n);

int main()
{
	struct name_count user_name;

	receive_input(&user_name);
	count_characters(&user_name);
	show_result(&user_name);

	return 0;
}

void receive_input(struct name_count* pter_nc)
{
	int flag;

	printf("Input your first name:\n>>");

	flag = scanf("%[^\n]%*c", pter_nc->first); // ^ : cap operator
	if (flag != 1)
		printf("Wrong input");

	printf("Input your last name:\n>>");

	flag = scanf("%[^\n]%*c", pter_nc->last);
	if (flag != 1)
		printf("Wrong input");
}

void count_characters(struct name_count* ptr_nc)
{
	ptr_nc->num = strlen(ptr_nc->first) + strlen(ptr_nc->last);
}

void show_result(const struct name_count* ptr_nc)
{
	printf("Hi, %s %s, Your name has %d characters.\n",
		ptr_nc->first, ptr_nc->last, ptr_nc->num);
}

위에건 포인터를 사용하는 방법

• 포인터를 사용하지 않고 반환값을 이용해서 만든 방법

#include <stdio.h>
#include <string.h>

#define NLEN 20

// 구조체와 함수 연습문제
// 나의 이름을 입력 받고 character수 와 함께 이름 출력

struct name_count
{
	char first[NLEN]; // first name
	char last[NLEN]; // last name
	int num;
};

struct name_count receive_input();
struct name_count count_characters(struct name_count);
void show_result(const struct name_count);
char* s_gets(char* st, int n);

int main()
{
	struct name_count user_name;

	user_name = receive_input();
	user_name = count_characters(user_name);
	show_result(user_name);

	return 0;
}

struct name_count receive_input()
{
	struct name_count nc;

	int flag;

	printf("Input your first name:\n>>");

	flag = scanf("%[^\n]%*c", nc.first); // ^ : cap operator
	if (flag != 1)
		printf("Wrong input");

	printf("Input your last name:\n>>");

	flag = scanf("%[^\n]%*c", nc.last);
	if (flag != 1)
		printf("Wrong input");
}

struct name_count count_characters(struct name_count nc)
{
	nc.num = strlen(nc.first) + strlen(nc.last);
}

void show_result(const struct name_count nc)
{
	printf("Hi, %s %s, Your name has %d characters.\n",
		nc.first, nc.last, nc.num);
}