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How to get the element by providing position in vector template?
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Element access: reference operator [g] – Returns a reference to the element at position 'g' in the vector. at(g) – Returns a reference to the element at position 'g' in the vector. front() – Returns a reference to the first element in the vector. back() – Returns a reference to the last element in the vector.
Access an element in vector using vector::at() reference at(size_type n); reference at(size_type n); It returns the reference of element at index n in vector. If index n is out of range i.e. greater then size of vector then it will throw out_of_range exception.
Use std::find_if() with std::distance() This is a recommended approach to finding an element in a vector if the search needs to satisfy a specific logic eg, finding an index of element in the vector that is a prime number using prime number logic.
You can do that using at. You can try out the following simple example: const size_t N = 20; std::vector<int> vec(N); try { vec.at(N - 1) = 7; } catch (std::out_of_range ex) { std::cout << ex. what() << std::endl; } assert(vec.at(N - 1) == 7);
You access std::vector elements just like a regular C array:
std::vector<int> myVector;
//(...)
int a = myVector[1];
You could use the 'at' function (someVector.at(somePosition) gets you the element at somePosition), or you could use someVector[somePosition]. It's like a more developed array.
The difference between using the at function is that it will throw an exception if you give it an invalid position, while the []s don't check for things like that.
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