Question

I need to go through this vector and delete the duplicates. A segmentation fault is occurring somewhere within this code. My guess is that it has something to do with deleting elements while the iterator is going through, but I don’t really have a concrete understanding of how these iterators are actually working yet, so I can’t figure it out.

vector<char *>::iterator iter;
for (iter = v->begin(); iter != v->end()-1; iter++ ){
    char *aString = *iter;
    int n = 1;
    while(iter+n != v->end()){
        int comparison = strcmp(aString, *(iter+n));
        if(comparison == 0){
            v->erase(iter + n);
        }
        n++;
    }
}

Answer 1

Really, you just have a couple off-by-one problems here. You were comparing incorrectly against end() and incrementing n when you erased an element:

for (iter = v->begin(); iter != v->end()-1; iter++ ){
                                  ^^^^^^^^

And

while(iter+n != v->end())
             ^^

The following will do what you want (and demonstrate that it works):

int main()
{

    std::vector<const char*> v (4, "this");
    std::vector<const char *>::iterator iter;

    for (iter = v.begin(); iter <  v.end(); iter++ ) {
        std::cout << *iter << " ";
    }
    std::cout << std::endl;

    for (iter = v.begin(); iter <  v.end(); iter++ ){
        const char *aString = *iter;
        int n = 1;
        while(iter+n < v.end()){
            int comparison = strcmp(aString, *(iter+n));
            if(comparison == 0){
                v.erase(iter + n);
            }
            else
                n++;
        }
    }

    for (iter = v.begin(); iter <  v.end(); iter++ ) {
        std::cout << *iter << std::endl;
    }

}

Output is:

this this this this

this