I'm new to vector in C++ and trying to get how it works. First, I have a vector array:
vector<int>container;
Then I want to get the position of a given number in a vector array.
vector<int>::iterator position;
position = lower_bound(container.begin(), container.end(), temp);
After that, I want to get the value at that position that was returned from lower_bound by
container[position]
But I get the error that
No viable overloaded operator[] for type 'vector'
When I change it into *(position+1), it works fine.
So what is the different between those two?
First of all, we should understand what an iterator is. According to the hackingcpp
- objects that point to a location
- may point to a readable memory address / object
- ..
There are a lot of containers in C++ STL, such as vector, list, map and others.
A iterator is an abstraction of pointer, which allows you to access elements stored in container, use algorithm(such as sort, find, lower_bound) provided by STL no matter what kind of container we have.
Therefore, the return type of std::lower_bound is an iterator as you know vector<int>::iterator,
You couldn't access an element by calling container[position], there is no such function vector[iterator] provided by vector.
When I change it into *(position+1)
*itreator means return the value of where an iterator points out.
By the way, it's dangerous to do something like this *(position+1).
Since perhaps the given value tmp is in vector, perhaps it's not, so you should check whether the given value tmp is in vector by calling iterator != vector.end().