Problem p02265 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <algorithm>
#include <cstdio>
#include <iostream>
#include <string>

using namespace std;

typedef struct n {
  int Key;
  n *prev, *next;
} Node;

Node *nil;
const string COMMAND[4] = {"insert", "deleteFirst", "deleteLast", "delete"};

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

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

void deleteNode(Node *t) {
  if (t == nil)
    return;
  t->next->prev = t->prev;
  t->prev->next = t->next;
  free(t);
}

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

void deletelast() { deleteNode(nil->prev); }

Node *SearchNode(int Key) {
  Node *ser;
  ser = nil->next;
  while (ser != nil && ser->Key != Key) {
    ser = ser->next;
  }
  return ser;
}

void delete_X(int Key) { deleteNode(SearchNode(Key)); }

void ReadCommand() {
  char comm[16];
  scanf("%s", comm);
  if (comm == COMMAND[0]) {
    int Key;
    scanf("%d", &Key);
    intsert(Key);
  } else if (comm == COMMAND[1]) {
    deletefirst();
  } else if (comm == COMMAND[2]) {
    deletelast();
  } else {
    int Key;
    cin >> Key;
    deleteNode(SearchNode(Key));
  }
}

void printNode() {
  Node *k;
  k = nil->next;
  while (k != nil) {
    if (k->next != nil) {
      printf("%d ", k->Key);
    } else {
      printf("%d\\n", k->Key);
    }
    k = k->next;
  }
}

int main() {
  init();
  int N;
  cin >> N;
  for (int i = 0; i < N; i++)
    ReadCommand();
  printNode();
  return 0;
}

Error: TLE

Fixed submission:

#include <algorithm>
#include <cstdio>
#include <iostream>
#include <string>

using namespace std;

typedef struct n {
  int Key;
  n *prev, *next;
} Node;

Node *nil;
const string COMMAND[4] = {"insert", "deleteFirst", "deleteLast", "delete"};

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

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

void deleteNode(Node *t) {
  t->next->prev = t->prev;
  t->prev->next = t->next;
  free(t);
}

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

void deletelast() { deleteNode(nil->prev); }

Node *SearchNode(int Key) {
  Node *ser;
  ser = nil->next;
  while (ser != nil && ser->Key != Key) {
    ser = ser->next;
  }
  return ser;
}

void delete_X(int Key) { deleteNode(SearchNode(Key)); }

void ReadCommand() {
  char comm[16];
  scanf("%s", comm);
  if (comm == COMMAND[0]) {
    int Key;
    scanf("%d", &Key);
    intsert(Key);
  } else if (comm == COMMAND[1]) {
    deletefirst();
  } else if (comm == COMMAND[2]) {
    deletelast();
  } else {
    int Key;
    cin >> Key;
    deleteNode(SearchNode(Key));
  }
}

void printNode() {
  Node *k;
  k = nil->next;
  while (k != nil) {
    if (k->next != nil) {
      printf("%d ", k->Key);
    } else {
      printf("%d\\n", k->Key);
    }
    k = k->next;
  }
}

int main() {
  init();
  int N;
  cin >> N;
  for (int i = 0; i < N; i++)
    ReadCommand();
  printNode();
  return 0;
}