Stack.c

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
struct Stack
{
	int size;
	int top;
	int* s;
};
void create(struct Stack* st)
{
	printf("Enter Size");
	scanf("%d", &st->size);
	st->top = -1;
	st->s = (int*)malloc(st->size * sizeof(int));
}
void Display(struct Stack st)
{
	int i;
	for (i = st.top; i >= 0; i--)
	{
		printf("%d ", st.s[i]);
	}
	printf("\n");
}
void push(struct Stack* st, int x)
{
	if (st->top == st->size - 1)
	{
		printf("Stack Overflow");
	}
	else
	{
		st->top++;
		st->s[st->top] = x;
	}
}
int pop(struct Stack* st)
{
	int x = -1;
	if (st->top == -1)
	{
		printf("Stack underflow\n");
	}
	else
	{
		x = st->s[st->top--];
	}
	return x;
}
int peek(struct Stack st, int pos)
{
	int x = -1;
	if (st.top - pos + 1 < 0)
	{
		printf("Invalid Position");
	}
	else
	{
		x = st.s[st.top - pos + 1];
	}
	return x;
}
int isEmpty(struct Stack st)
{
	if (st.top == -1)
		return 1;
	return 0;
}
int isFull(struct Stack st)
{
	return st.top == st.size - 1;
}
int stackTop(struct Stack st)
{
	if (!isEmpty(st))
		return st.s[st.top];
	return -1;
}
int main()
{
	struct Stack st;
	create(&st);
	push(&st, 10);
	push(&st, 20);
	push(&st, 30);
	push(&st, 40);
	push(&st, 50);
	printf("%d \n", peek(st, 2));
	Display(st);
	printf("%d \n", pop(&st));
	return 0;
}