Question

How to update the value of a key in std::map after using the find method?

I have a map and iterator declaration like this:

map <char, int> m1;
map <char, int>::iterator m1_it;
typedef pair <char, int> count_pair;

I’m using the map to store the number of occurrences of a character.

I’m using Visual C++ 2010.

Answer 1

std::map::find returns an iterator to the found element (or to the end() if the element was not found). So long as the map is not const, you can modify the element pointed to by the iterator:

std::map<char, int> m;
m.insert(std::make_pair('c', 0));  // c is for cookie

std::map<char, int>::iterator it = m.find('c'); 
if (it != m.end())
    it->second = 42;