Checking whether an element exist or not in the map within map

Question

I have a map of the form map > :

For Example: I am storing the intensity value at 2-D co-ordinate(x,y) i

Answer 1

You can use std::map::find and check if the element exists before accessing it. You can read the usage/documentation here: http://en.cppreference.com/w/cpp/container/map/find