how to delete from list

This is a discussion on how to delete from list within the C++ Programming forums, part of the General Programming Boards category; Code: class Person{ public: string name; string address; string phone; public: friend ostream& operator<< (ostream& out,const Person& person){ out.setf(ios::left); out.width(sizeof(person.name)+6); ...

  1. #1
    Registered User
    Join Date
    Dec 2006
    Posts
    1

    Question how to delete from list

    Code:
    class Person{  
          public:
                 string name;
                 string address;
                 string phone;
          
          public:
                 friend ostream& operator<< (ostream& out,const Person& person){
                        out.setf(ios::left);
                        out.width(sizeof(person.name)+6);
                        out<<person.name;
                        out.width(sizeof(person.address)+6);
                        out<<person.address;
                        out.width(sizeof(person.phone));
                        out<<person.phone<<endl;
                        return out;
                        } 
                  friend istream& operator>> (istream& in, Person& person){
                         in.width(sizeof(person.name)+6);
    	                 in>>person.name;
    	                 in.width(sizeof(person.address)+6);
    	                 in>>person.address;
    	                 in.width(sizeof(person.phone)+6);
    	                 in>>person.phone;
                         return in; 
                         }
    };      
    
    list<Person> L;                                          
    list<Person>::iterator i;  
    
    bool find (Person pers, const list<Person> &L){
         
         for(list<Person>::const_iterator i = L.begin(); i != L.end(); ++i){
             if(((Person)*i).name == pers.name ){
                return true;
             }
         }   
    }
    
    void deleteR(){
         
                       Person person;
                              cout<<"\nEnter name: ";
                              cin>>person.name;
                              
                              if(find(person,L)){
                                        remove(person);  dont work...
                                          
                              }
                            
    }
    how i can.. delete from list..??plz help
    Last edited by Aljena; 12-13-2006 at 07:15 AM.

  2. #2
    Registered User
    Join Date
    Jan 2005
    Location
    Estonia
    Posts
    131
    you have to have the iterator you want to delete and then you type:

    L.erase(pos); where L is the list and pos is the iterator (not const_iterator).

    e.g.:
    list<int> L;
    L.push_back(4);
    L.push_back(3);
    list<int>::iterator pos;
    pos = L.begin(); //returns the iterator of the first element
    L.erase(pos); //erase the element that the iterator points to
    cout << L.size() << ' ' << *(L.begin()) << endl; //should output 1 3

  3. #3
    Registered User
    Join Date
    Dec 2006
    Posts
    30
    if you wanted to remove all occurrences of Persons with that name, you could do
    Code:
         for(list<Person>::iterator i = L.begin(); i != L.end();){
             if(i->name == person.name ){
                i = L.erase(i);
             } else {
                ++i;
             }
         }
    or just the first occurrence
    Code:
         for(list<Person>::iterator i = L.begin(); i != L.end(); ++i){
             if(i->name == person.name ){
                L.erase(i);
                break;
             }
         }
    you get the idea

    also, if you need to look up by person's name a lot, and don't need the order, you might consider using a map instead of a list

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