up_down.c

//https://thehuxley.com/problem/2133?quizId=6095
#include <stdio.h>
#include <string.h>
#define MAX_LENGHT 1000

typedef struct node
{
    char linha[MAX_LENGHT];
    NODE* next;
}NODE;

typedef struct stack
{
    NODE* top;
}STACK;

typedef struct string
{
    string[MAX_LENGHT];
}STR;

STACK* init_stack()//é chamado sem argumentos e cria um stack
{
    STACK* new_stack = (STACK*) malloc(sizeof(STACK));
    new_stack->top = NULL;
    return new_stack;   //retorna um novo_stack para ser usado
}

void push(STACK *stack, char *item)//como o topo é unico para todo o stack, só preciso mostrar o topo
{
    NODE *new_top = (NODE*) malloc(sizeof(NODE)); //aloca espaço para um novo nó
    strcpy(stack->top->linha, item);
    new_top->next = stack->top;
    stack->top = new_top;
}

int is_empty(STACK* stack)
{
    if (stack->top == NULL)
    {
        return 1;
    }
    return 0;
}

STR* pop(STACK *stack)
{
    STR *pooped = stack->top->linha;
    stack->top = stack->top->next;
    free(stack->top);
    return pooped;
}

int main()
{
    char linha1[MAX_LENGHT];
    int p = scanf("%s", linha1);
    STACK* stack = init_stack();
    while (p != EOF)
    {
        push(stack, linha1);
    }
    while (is_empty(stack)!= 1)
    {
        char out[MAX_LENGHT]
        STR* temp;
        temp = pop(stack);
        strcpy(linha1, tmp);
        fputs(out,stdout);
    }

    return 0;

}