Check if a key is present in a C++ map or unordered_map

In C++ the Maps and unordered maps are hash tables. They use some keys and their respective key values. Here we will see how to check whether a given key is present in the hash table or not. The code will be like below −

Example

 Live Demo

#include<iostream> #include<map> using namespace std; string isPresent(map<string, int> m, string key) {    if (m.find(key) == m.end())    return "Not Present";    return "Present"; } int main() {    map<string, int> my_map;    my_map["first"] = 4;    my_map["second"] = 6;    my_map["third"] = 6;    string check1 = "fifth", check2 = "third";    cout << check1 << ": " << isPresent(my_map, check1) << endl;    cout << check2 << ": " << isPresent(my_map, check2); }

Output

fifth: Not Present third: Present