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  1. #include <iostream>
  2. #include <list>
  3. using namespace std;
  4.  
  5. class D {
  6.  typedef list<int> L;
  7.  L* result;
  8.  L::iterator ptr;
  9.  public:
  10.    D() : result(0) {}
  11.    ~D() { delete result; }
  12.  
  13.    void make_result () {
  14.      result = new L;
  15.      for (int i=0; i < 5; ++ i)
  16.         result->push_back (i);
  17.      ptr = result->begin();
  18.    }
  19.  
  20.    void prev () { 
  21.       if (result == 0) return;
  22.       if (ptr == result->begin()) ptr = result->end (); 
  23.       --ptr; 
  24.    }
  25.  
  26.    void next () { 
  27.       if (result == 0) return;
  28.       if (++ptr == result->end()) ptr = result->begin (); 
  29.    }
  30.    void display () {
  31.       if (result == 0) return;
  32.       cout << *ptr << ' ';
  33.    }
  34. };
  35.  
  36. int main () {
  37.   D d;
  38.   d.display (); // output nothing
  39.   cout << endl;
  40.  
  41.   d.make_result();
  42.   for (int i=0; i < 10; ++i) {
  43.     d.next();
  44.     d.display();
  45.   }
  46.   cout << endl;
  47.  
  48.   for (int i=0; i < 10; ++i) {
  49.     d.prev();
  50.     d.display();
  51.   }
  52.   cout << endl;
  53. }
Success #stdin #stdout 0s 3228KB
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stdin
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Standard input is empty
stdout
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1 2 3 4 0 1 2 3 4 0 
4 3 2 1 0 4 3 2 1 0
https://ideone.com/fm9niY
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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