Why do I get a segmentation fault while iterating through this vector?

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++ )开发者_如何转开发{
    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++;
    }
}

---

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

---

You are not properly iterating through the remainder of the vector. An alternative to what Beta suggested is to use erase-remove with remove_if. Like this:

bool compare_strings(char * aString,char * bString)
{
    return 0==strcmp(aString,bString);
}

void remove_duplicates(vector<char *> * v)
{
    vector<char *>::iterator iter;
    for (iter = v->begin(); iter != v->end(); iter++ ) {
        v->erase(std::remove_if(iter+1,v->end(),compare_strings),v->end());
    }
}

---

When you erase an element from the vector, the vector gets one element shorter. Try this:

if(comparison == 0){
  v->erase(iter + n);
}
else{
  n++;
}

---

Erasing from a vector invalidates all iterators from the erasee onwards, so you should probably not construct your loop the way you do, and rather use a standard idiom like this:

for (auto it = v.begin(); it != v.end(); ++it)   // no end() - 1 -- may not be legal!
{
  for (auto jt = it; jt != v.end(); )
  {
    if (jt == it) continue;

    if (strcmp(*it, *jt) == 0)
    {
      jt = v.erase(jt);
    }
    else
    {
      ++jt;
    }
  }
}

This code avoids the check for an empty vector, which your code fails to account for.