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  1. #include <iostream>
  2. #include <string>
  3. #include <exception>
  4. using namespace std;
  5.  
  6. struct node{
  7.     int value;
  8.     node *next;
  9.     node():value(0), next(NULL){}
  10.     node(int value, node *next)
  11.     :value(value), next(next){}
  12. };
  13.  
  14. struct _queue{
  15.     int _size;
  16.     node *first;
  17.     node *last;
  18.     _queue():_size(0), first(NULL), last(NULL){}
  19.  
  20.     void push (int v){
  21.         node *new_node = new node(v, last);
  22.         if(_size == 0){
  23.             first = last = new_node;
  24.         }
  25.         else{
  26.             last->next = new_node;
  27.             last = new_node;
  28.         }
  29.         _size++;
  30.     }
  31.  
  32.     void pop(){
  33.         if (_size > 0){
  34.             int val = first->value;
  35.             first = first->next;
  36.             _size--;
  37.             cout << val;
  38.         }
  39.         else throw 0;
  40.     }
  41.  
  42.     void front(){
  43.         if (_size > 0) cout << first->value;
  44.         else throw 0;
  45.     }
  46.  
  47.     int size(){
  48.         return _size;
  49.     }
  50.  
  51.     void clear(){
  52.         while (_size > 0){
  53.             node *new_node = first->next;
  54.             delete first;
  55.             first = new_node;
  56.             _size--;
  57.         }
  58.         first = NULL;
  59.         last = NULL;
  60.     }
  61. };
  62.  
  63.  
  64. int main()
  65. {
  66.     _queue q;
  67.     string s;
  68.     int n;
  69.     while (cin >> s){
  70.         if (s == "size"){
  71.             cout << q.size() << endl;
  72.         }
  73.         if (s == "push"){
  74.             cin >> n;
  75.             q.push(n);
  76.             cout << "ok" << endl;
  77.         }
  78.         if (s == "pop"){
  79.             try{
  80.                 q.pop();
  81.             }
  82.             catch(int e){cout << "error";}
  83.             cout << endl;
  84.         }
  85.         if (s == "front"){
  86.             try {
  87.                 q.front();
  88.             }
  89.             catch(int e){cout << "error";}
  90.             cout<<endl;
  91.         }
  92.         if (s == "clear"){
  93.             q.clear();
  94.             cout << "ok" << endl;
  95.         }
  96.         if (s == "exit"){
  97.             cout << "bye" <<endl;
  98.             return 0;
  99.         }
  100.     }
  101.     return 0;
  102. }
Success #stdin #stdout 0s 3420KB
comments (?)
stdin 
size
push 1
size
push 2
size
push 3
size
exit
stdout 
0
ok
1
ok
2
ok
3
bye
https://ideone.com/9tooRU
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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