unordered_map c++ insert

// C++ program to demonstrate functionality of unordered_map 
#include <iostream> 
#include <unordered_map> 
using namespace std; 
  
int main() 
{ 
    // Declaring umap to be of <string, int> type 
    // key will be of string type and mapped value will 
    // be of double type 
    unordered_map<string, int> umap; 
  
    // inserting values by using [] operator 
    umap["GeeksforGeeks"] = 10; 
    umap["Practice"] = 20; 
    umap["Contribute"] = 30; 
  
    // Traversing an unordered map 
    for (auto x : umap) 
      cout << x.first << " " << x.second << endl; 
  
} 

// C++ program to illustrate 
// unordered_map::insert({key, element}) 
#include <bits/stdc++.h> 
using namespace std; 
  
int main() 
{ 
    // initialize container 
    unordered_map<int, int> ump; 
  
    // insert elements in random order 
    ump.insert({ 20, 130 }); 
    ump.insert({ 100, 410 }); 
    ump.insert({ 31, 60 }); 
  
    // prints the elements 
    cout << "KEY\tELEMENT\n"; 
    for (auto itr = ump.begin(); itr != ump.end(); itr++) { 
        cout << itr->first 
             << '\t' << itr->second << '\n'; 
    } 
    return 0; 
} 

// unordered_map::insert
#include <iostream>
#include <string>
#include <unordered_map>

int main ()
{
  std::unordered_map<std::string,double>
              myrecipe,
              mypantry = {{"milk",2.0},{"flour",1.5}};

  std::pair<std::string,double> myshopping ("baking powder",0.3);

  myrecipe.insert (myshopping);                        // copy insertion
  myrecipe.insert (std::make_pair<std::string,double>("eggs",6.0)); // move insertion
  myrecipe.insert (mypantry.begin(), mypantry.end());  // range insertion
  myrecipe.insert ( {{"sugar",0.8},{"salt",0.1}} );    // initializer list insertion

  std::cout << "myrecipe contains:" << std::endl;
  for (auto& x: myrecipe)
    std::cout << x.first << ": " << x.second << std::endl;

  std::cout << std::endl;
  return 0;
}

#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;
}