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

typedef struct Number {
    int num;
    struct Number *nxt;
} Number;

Number *list_toend(Number *list, int what) {
    Number *newel = (Number*) malloc(sizeof(Number));
    newel->num = what;
    newel->nxt = NULL;
    if (list == NULL)
        return newel;
    else {
        Number *iter;
        for (iter = list; iter->nxt != NULL; iter = iter->nxt)
            ; /* empty for loop */
        iter->nxt = newel;
        return list;
    }
}

/* Reverses a linked list and 
    * returns the pointer to the head of the reversed one.
    * Attention: the original list will be gone! The function uses
    * the elements of the original list to build the reversed one.
    * Usage:
    *   numbers = list_reverse(numbers);
    */
Number *list_reverse(Number *list) {
    Number *original = list;
    Number *reversed = NULL;
 
    while (original != NULL) {
        Number *relinked = original, *next = original->nxt;
        relinked->nxt = reversed;   /* add to the reversed */ /* 1 */
        reversed = relinked;                                     /* 2 */
        original = next;               /* take next fro morig.*/ /* 3 */
    }
 
    return reversed;
}

void list_print(Number *list) {
    Number *iter;
    for (iter = list; iter != NULL; iter = iter->nxt)
        printf("%d ", iter->num);
    printf("\n");
}

void list_free(Number *list) {
    while (list != NULL) {
        Number *nxt = list->nxt;
        free(list);
        list = nxt;
    }
}

int main(void) {
    Number *list = NULL;
    int n;

    printf("Enter numbers, I will put them to a list. Enter 0 to finish.\n");
    printf("Then I print it, reverse it, and print the reversed one.\n");
    scanf("%d", &n);
    while (n != 0) {
        list = list_toend(list, n);
        scanf("%d", &n);
    }

    list_print(list);

    list = list_reverse(list);

    list_print(list);

    list_free(list);

    return 0;
}