tp 9.6

#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <stdlib.h>
#define NMAX 1001

void checkAlloc(const void *const p) {
  if (p == NULL) {
    perror("");
    exit(EXIT_FAILURE);
  }
}

typedef struct Node {
  char text[NMAX];
  struct Node *prev, *next;
} Node;

Node *newNode(const char s[NMAX]) {
  Node *node = malloc(sizeof(Node));
  checkAlloc(node);
  node->next = node->prev = NULL;
  strcpy(node->text, s);
  return node;
}

typedef struct {
  Node *first, *last;
} List;

void initList(List *list) {
  list->first = list->last = NULL;
}

void printList(const List *const list) {
  for (Node *it = list->first; it; it = it->next) {
    fputs(it->text, stdout);
  }
  fputc('\n', stdout);
}

void freeList(List *list) {
  Node *next;
  for (Node *it = list->first; it; it = next) {
    next = it->next;
    free(it);
  }
}

void addEnd(List *list, const char text[NMAX]) {
  Node *node = newNode(text);
  if (!list->last) {
    list->first = list->last = node;
    return;
  }
  list->last->next = node;
  node->prev = list->last;
  list->last = node;
}

void moveLastAtStart(List *list) {
  if (!list->first || list->first == list->last) {
    return;
  }
  Node *last = list->last;
  list->last->prev->next = NULL;
  last->prev = NULL;
  last->next = list->first;
  list->first = last;
}

int main() {
  List list;
  initList(&list);

  int n;
  scanf("%d", &n);
  getchar();
  static char s[NMAX];
  for (int i = 0; i < n; i++) {
    if (fgets(s, NMAX, stdin) == NULL) {
      perror("");
      exit(1);
    }
    addEnd(&list, s);
  }
  moveLastAtStart(&list);
  printList(&list);
  freeList(&list);
  return 0;
}