c++ unordered_map contains code example

Example 1: cpp unordered_map has key

// Function to check if the key is present or not
string check_key(map<int, int> m, int key)
{
    // Key is not present
    if (m.find(key) == m.end())
        return "Not Present";
  
    return "Present";
}

Example 2: unordered_map c++

#include <bits/stdc++.h>
#include <iostream>
#include <map>
#include <unordered_map>

using namespace std;

int main() {
  	map<char, int> M; //based on balanced binary tree takes O(logn) access time
	unordered_map<char, int> U; //uses hashing and accessing elements takes O(1)
	//U.add(key,value);
  	//U.erase(key,value);
  	
  	//map each letter to their occurance
  	string s = "Sumant Tirkey";
  	for (char c : s) {
  		M[c]++;
	  }
	for (char c : s){
		U[c]++;
	}
  
  return 0;
}