Tuple Vector iteration, element access and erasion

[ktsangop]

Hello everyone!
I would like your help regarding this:
I have a tuple vector which i must iterate through, and accessing the vector data to decide wether to erase or not the current vector element.
My code :

typedef tuple <int, CString, int, int> pc_data;
vector <pc_data> pc_vec;

//Assume that pc_vec is filled with elements somewhere here...


//This code is not working. 
//Exception : vector subject out of range because of the size dynamically changing i suppose
for (int i=0; i<num_of_pcs; i++)
{
    if(std::get<2>(pc_vec[i])==0)
        pc_vec.erase(pc_vec.begin()+i);
}

//second try
//No exception here but the dynamic size of the vector again won't let me access all elements sequentially
for (size_t i = 0; i < pc_vec.size(); i++)
{
    if(std::get<2>(pc_vec[i])==0)
        pc_vec.erase(pc_vec.begin()+i);
}

//third try
//use iterator
vector<pc_data>::iterator it = pc_vec.begin();
//I don't know how to access the current element data in this situation..(?)
for ( ; it != pc_vec.end(); ) 
{
    if(std::get<2>(/*WHAT SHOULD I USE TO ACCESS THE CURRENT ELEMENT HERE??*/)==0)
    {
        it = pc_vec.erase(it);
    } 
    else 
    {
        ++it;
    }
}

Could you please suggest me a way to do it?
Thanks in advance and hope my question is clear enough.

[Gonbe]

Do you mean something like this?

#include <iostream>
#include <tuple>
#include <vector>
#include <string>

using namespace std;

int main()
{
    typedef tuple <int, string, int, int> pc_data;

    vector <pc_data> pc_vec;

    // Add some test data
    pc_vec.push_back(make_tuple(0, "never gonna ", 0, 0));
    pc_vec.push_back(make_tuple(1, "give you ", 1, 0));
    pc_vec.push_back(make_tuple(2, "up, never ", 2, 0));
    pc_vec.push_back(make_tuple(3, "stop. HAMMER TIME.", 3, 0));
    pc_vec.push_back(make_tuple(4, "gonna let you ", 4, 0));
    pc_vec.push_back(make_tuple(5, "down.\n", 5, 0));

    //Assume that pc_vec is filled with elements somewhere here...
    //This code is not working.
    //Exception : vector subject out of range because of the size dynamically changing i suppose
    for (int i=0; i < pc_vec.size(); i++)
    {
        // Test: we're going to delete the tuple of which the 3rd element (index 2) = 3.
        if(get<2>(pc_vec[i]) == 3)
        {
            pc_vec.erase(pc_vec.begin() + i);
            i--;
        }
    }

    // Result:
    for (int i = 0; i < pc_vec.size(); i++)
    {
        cout << get<1>(pc_vec[i]);
    }

    return 0;
}

[ktsangop]

Awww! Why didn't i think of that???!!
:)
Thanks a lot that seems to work!

By the way is there any reason that someone should use an iterator for this? Would it be more secure or fast?

Thanks again!

[Gonbe]

By the way is there any reason that someone should use an iterator for this? Would it be more secure or fast?

The main benefit (as far as I know) is that the use of iterators makes your code generic because most (if not all) containers in the STL support it. Performance differences seem to vary, never really tested it myself.

[ktsangop]

Thank you Gonbe!

[NathanOliver]

Just as an FYI. If you call erase on a vector and you are using iterators any iterator that is after the begining will be invalidated.

[ktsangop]

Nice to know. I should read about iterator invalidation rules i suppose... my STL knowledge needs to be refreshed as it seems like i forgot everything...
:D