Using push_back on a vector

Question

I'm somewhat embarrassed that such a simple problem has stymied me, but after a few hours of fruitless googling, I'm still stuck. To simplify my problem, the 2nd line of this crashes: ``` vector > sorted_words; sorted_words[0].push_back("hello"); ``` Shouldn't `sorted_words[0]` represent an empty vector that I can legally push_back onto?

Accepted Answer

No. You have a vector of vectors. You haven't added anything to either vector by line 2, so `sorted_words[0]`, the first element in `sorted_words`, doesn't exist yet. You're trying to push `"hello"` into a null `vector`. Null pointer dereference! I would ask "do you really want a vector of vectors, or just a vector of strings"? If you want a vector of strings, then use: ``` vector sorted_words; sorted_words.push_back("hello"); ``` If you really do want a vector of vectors (of strings), then use: ``` vector first_vector; first_vector.push_back("hello"); sorted_words.push_back(first_vector); ```

Using push_back on a vector<vector<string> >

Solution

Problem