스택(Stack)

Last In First Out(LIFO) 구조

#include <stdio.h>

#define SIZE 100

typedef enum eSelectMenu { 
	selectPush = 1,
	selectPop,
	selectPeek,
	selectSize,
	selectExit
} eSelectMenu;

typedef enum eBool{
	false,
	true
} eBool;

int top = -1;	// -1 or 0
int stack[SIZE];

void Push(int data) {
	stack[++top] = data;
}

int Pop() {
	return stack[top--];
}

eBool IsEmpty() {
	return top == -1 ? true : false;
}

eBool IsFull() {
	return top + 1 == SIZE ? true : false;
}

int Peek() {
	return stack[top];
}

int Size() {
	return top + 1;
}

int main(void) {
	eSelectMenu select;
	int data;

	while (1) {
		printf("1. push / 2. pop / 3. peek / 4. size / 5. exit\n");
		printf("select: ");
		scanf_s("%d", &select);
		
		switch (select) {
		case selectPush:
			if (IsFull() == true) {
				printf("stack full\n\n");
				break;
			}
			printf("data: ");
			scanf_s("%d", &data);
			Push(data);
			printf("\n");
			break;
		case selectPop:
			if (IsEmpty() == true) {
				printf("stack empty\n\n");
				break;
			}
			printf("return data: %d\n\n", Pop());
			break;
		case selectPeek:
			if (IsEmpty() == true) {
				printf("stack empty\n\n");
				break;
			}
			printf("last data: %d\n\n", Peek());
			break;
		case selectSize:
			printf("current stack size: %d\n\n", Size());
			break;
		case selectExit:
			printf("exit program\n");
			return 0;
		default:
			printf("re\n\n");
		}
		while(getchar() != '\n') {}
	}
}

top 의 초기 값이 -1 or 0 인지에 따라 push, pop 전, 후위 증감 연산 위치가 달라야 한다.