Problem p02265 (C++) — buggy submission, verdict: Runtime Error

#define _CRT_SECURE_NO_WARNINGS

#include <cstdio>
#include <cstdlib> //?????????????????????????????????C???scanf????????¨????????????
#include <cstring>
#include <iostream>
#include <string>
using namespace std;

struct Node {
  int key;
  Node *prev, *next;
};

Node *nil;

void init() {
  nil = (Node *)malloc(sizeof(Node));
  nil->next = nil; //->???????????????????????????????????¢?????????
  nil->prev = nil;
}

void insert(int key) {
  Node *x = (Node *)malloc(sizeof(Node));
  x->key = key;
  x->next = nil->next;
  nil->next->prev = x;
  nil->next = x;
  x->prev = nil;
}

Node *listSearch(int key) {
  Node *cur = nil->next;
  while (cur != nil && cur->key != key) {
    cur = cur->next;
  }
  return cur;
}

//???????????¨?????????????????????????\\???????
void deleteNode(Node *t) {
  if (t == nil)
    return; // t??????????????¨?????????
  t->prev->next = t->next;
  t->next->prev = t->prev;
  free(t); //?????¨????????????????????¬??????????????????????§£???
}

void deleteFirst() { deleteNode(nil->next); }

void deleteLast() {
  deleteNode(nil->prev); //?????????????????????????°?
}

void deleteKey(int key) { deleteNode(listSearch(key)); }

void Print() {
  Node *n = nil->next;
  int ifs = 0;
  while (1) {
    if (n == nil)
      break;
    if (ifs++ > 0)
      printf(" ");
    printf("%d", n->key);
    n = n->next;
  }
  printf("\\n");
}

int main() {
  int n, data;
  scanf("%d", &n);
  char command[20];
  init(); //?±???????????????????????????????
  for (int i = 0; i < n; i++) {
    scanf("%s%d", command, &data);
    if (command[0] == 'i') {
      insert(data);
    } else if (strlen(command) == 6) {
      deleteKey(data);
    } else if (command[6] == 'F') {
      deleteFirst();
    } else {
      deleteLast();
    }
  }

  Print();
}

Error: -11

Fixed submission:

#define _CRT_SECURE_NO_WARNINGS

#include <cstdio>
#include <cstdlib> //?????????????????????????????????C???scanf????????¨????????????
#include <cstring>
#include <iostream>
#include <string>
using namespace std;

struct Node {
  int key;
  Node *prev, *next;
};

Node *nil;

void init() {
  nil = (Node *)malloc(sizeof(Node));
  nil->next = nil; //->???????????????????????????????????¢?????????
  nil->prev = nil;
}

void insert(int key) {
  Node *x = (Node *)malloc(sizeof(Node));
  x->key = key;
  x->next = nil->next;
  nil->next->prev = x;
  nil->next = x;
  x->prev = nil;
}

Node *listSearch(int key) {
  Node *cur = nil->next;
  while (cur != nil && cur->key != cur->key) {
    cur = cur->next;
  }
  return cur;
}

//???????????¨?????????????????????????\\???????
void deleteNode(Node *t) {
  if (t == nil)
    return; // t??????????????¨?????????
  t->prev->next = t->next;
  t->next->prev = t->prev;
  free(t); //?????¨????????????????????¬??????????????????????§£???
}

void deleteFirst() { deleteNode(nil->next); }

void deleteLast() {
  deleteNode(nil->prev); //?????????????????????????°?
}

void deleteKey(int key) { deleteNode(listSearch(key)); }

void Print() {
  Node *n = nil->next;
  int ifs = 0;
  while (1) {
    if (n == nil)
      break;
    if (ifs++ > 0)
      printf(" ");
    printf("%d", n->key);
    n = n->next;
  }
  printf("\\n");
}

int main() {
  int n, data;
  cin >> n;
  char command[20];
  for (int i = 0; i < n; i++) {
    scanf("%s", command);
    if (command[0] == 'i') {
      scanf("%d", &data);
      insert(data);
    } else if (strlen(command) == 6) {
      scanf("%d", &data);
      deleteKey(data);
    } else if (command[6] == 'F') {
      deleteFirst();
    } else {
      deleteLast();
    }
  }

  Print();
}