Adding to middle of std::vector

问题:

Is there a way to add values to the middle of a vector in C++? Say I have:

vector <string> a;
// a gets filled up with "abcd", "wertyu", "dvcea", "eafdefef", "aeefr", etc

and I want to break up one of the strings and put all of the pieces back into the vector. How would I do that? the strings I break can be anywhere, index = 0, somewhere in the middle, or index = a.size() - 1.

回答1:

You can insert into a vector at position i by writing

v.insert(v.begin() + i, valueToInsert);

However, this isn't very efficient; it runs in time proportional to the number of elements after the element being inserted. If you're planning on splitting up the strings and adding them back in, you are much better off using a std::list, which supports O(1) insertion and deletion everywhere.

回答2:

You can do that, but it will be really slow:

int split = 3; // where to split
a.insert(a.begin()+index, a[index].substr(0, split));
a[index+1] = a[index+1].substr(split);