Language: C++

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
using namespace std;

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

Node *nil;

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

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

void printList(){
	Node *cur = nil->next;
	int isf = 0;
	while (1){
		if (cur == nil) break;
		// if (isf++ > 0) printf(" ");
		if (isf++ > 0) cout << " ";
		// printf("%d", cur->key);
		cout << cur->key;
		cur = cur->next;
	}
	printf("\n");
}

void deleteNode(Node *t){
	if (t == nil) return;
	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 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;
}

int main(){
	int key, n, i;
	int size = 0;
	char com[20];
	int np = 0, nd = 0;
	scanf("%d", &n);
	//cin >> &n;
	init();
	for (i = 0; i < n; i++){
		// scanf("%s%d", com, &key);
		cin >> com >> &key;
		if (com[0] == 'i'){ insert(key); np++; size++; }
		else if (com[0] == 'd'){
			if (strlen(com) > 6){
				if (com[6] == 'F') deleteFirst();
				else if (com[6] == 'L') deleteLast();
			} else {
				deleteKey(key); nd++;
			}
			size--;
		}
	}

	printList();

	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:82:28: error: no match for 'operator>>' (operand types are 'std::basic_istream<char>' and 'int*')
   82 |                 cin >> com >> &key;
      |                 ~~~~~~~~~~ ^~ ~~~~
      |                     |         |
      |                     |         int*
      |                     std::basic_istream<char>
In file included from /usr/include/c++/14/iostream:42,
                 from a.cc:4:
/usr/include/c++/14/istream:170:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  170 |       operator>>(bool& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:170:7: note:   conversion of argument 1 would be ill-formed:
a.cc:82:31: error: cannot bind non-const lvalue reference of type 'bool&' to a value of type 'int*'
   82 |                 cin >> com >> &key;
      |                               ^~~~
/usr/include/c++/14/istream:174:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  174 |       operator>>(short& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:174:7: note:   conversion of argument 1 would be ill-formed:
a.cc:82:31: error: invalid conversion from 'int*' to 'short int' [-fpermissive]
   82 |                 cin >> com >> &key;
      |                               ^~~~
      |                               |
      |                               int*
a.cc:82:31: error: cannot bind rvalue '(short int)(& key)' to 'short int&'
/usr/include/c++/14/istream:177:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  177 |       operator>>(unsigned short& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:177:7: note:   conversion of argument 1 would be ill-formed:
a.cc:82:31: error: invalid conversion from 'int*' to 'short unsigned int' [-fpermissive]
   82 |                 cin >> com >> &key;
      |                               ^~~~
      |                               |
      |                               int*
a.cc:82:31: error: cannot bind rvalue '(short unsigned int)(& key)' to 'short unsigned int&'
/usr/include/c++/14/istream:181:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  181 |       operator>>(int& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:181:7: note:   conversion of argument 1 would be ill-formed:
a.cc:82:31: error: invalid conversion from 'int*' to 'int' [-fpermissive]
   82 |                 cin >> com >> &key;
      |                               ^~~~
      |                               |
      |                               int*
a.cc:82:31: error: cannot bind rvalue '(int)(& key)' to 'int&'
/usr/include/c++/14/istream:184:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  184 |       operator>>(unsigned int& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:184:7: note:   conversion of argument 1 would be ill-formed:
a.cc:82:31: error: invalid conversion from 'int*' to 'unsigned int' [-fpermissive]
   82 |                 cin >> com >> &key;
      |                               ^~~~
      |                               |
      |                               int*
a.cc:82:31: error: cannot bind rvalue '(unsigned int)(& key)' to 'unsigned int&'
/usr/include/c++/14/istream:188:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  188 |       operator>>(long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:188:7: note:   conversion of argument 1 would be ill-formed:
a.cc:82:31: error: invalid conversion from 'int*' to 'long int' [-fpermissive]
   82 |                 cin >> com >> &key;
      |                               ^~~~
      |                               |
      |                               int*
a.cc:82:31: error: cannot bind rvalue '(long int)(& key)' to 'long int&'
/usr/include/c++/14/istream:192:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  192 |       operator>>(unsigned long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:192:7: note:   conversion of argument 1 would be ill-formed:
a.cc:82:31: error: invalid conversion from 'int*' to 'long unsigned int' [-fpermissive]
   82 |                 cin >> com >> &key;
      |                               ^~~~
      |                               |
      |                               int*
a.cc:82:31: error: cannot bind rvalue '(long unsigned int)(& key)' to 'long unsigned int&'
/usr/include/c++/14/istream:199:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  199 |       operator>>(long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:199:7: note:   conversion of argument 1 would be ill-formed:
a.cc:82:31: error: invalid conversion from 'int*' to 'long long int' [-fpermissive]
   82 |                 cin >> com >> &key;
      |                               ^~~~
      |                               |
      |                               int*
a.cc:82:31: error: cannot bind rvalue '(long long int)(& key)' to 'long long int&'
/usr/include/c++/14/istream:203:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  203 |       operator>>(unsigned long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:203:7: note:   conversion of argument 1 would be ill-formed:
a.cc:82:31: error: invalid conversion from 'int*' to 'long long unsigned int' [-fpermissive]
   82 |                 cin >> com >> &key;
      |                               ^~~~
      |                               |
      |                               int*
a.cc:82:31: error: cannot bind rvalue '(long long unsigned int)(& key)' to 'long long unsigned int&'
/usr/include/c++/14/istream:328:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  328 |       operator>>(void*& __p)
      |       ^~~~~~~~
/usr/include/c++/14/istream:328:7: note:   conversion of argument 1 would be ill-formed:
a.cc:82:31: error: cannot bind non-const lvalue reference of type 'void*&' to an rvalue of type 'void*'
   82 |                 cin >> com >> &key;
      |                               ^~~~
/usr/include/c++/14/istream:219:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  219 |       operator>>(float& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:219:25: note:   no known conversion for argument 1 from 'int*' to 'float&'
  219 |       operator>>(float& __f)
      |                  ~~~~~~~^~~
/usr/include/c++/14/istream:223:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  223 |       operator>>(double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:223:26: note:   no known conversion for argument 1 from 'int*' to 'double&'
  223 |       operator>>(double& __f)
      |                  ~~~~~~~~^~~
/usr/include/c++/14/istream:227:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  227 |       operator>>(long double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:227:31: note:   no known conversion for argument 1 from 'int*' to 'long double&'
  227 |       operator>>(long double& __f)
      |                  ~~~~~~~~~~~~~^~~
/usr/include/c++/14/istream:122:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__istream_type& (*)(__istream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  122 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:122:36: note:   no known conversion for argument 1 from 'int*' to 'std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&)' {aka 'std::basic_istream<char>& (*)(std::basic_istream<char>&)'}
  122 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |                  ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/istream:126:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__ios_type& (*)(__ios_type&)) [with _CharT = char; _Traits = std::char_tra