startswith()
std::string s = "tititoto";
if (s.rfind("titi", 0) == 0) {
// s starts with prefix
}
collections,Counter()
std::vector<int> v = { 7, 2, 2, 4, 3, 2, 6 };
int val = 2;
int freq = std::count(v.begin(), v.end(), val);
std::cout << "Element " << val << " occurs " << freq << " times";