how to iterate over unordered_map c++

// 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; 
  
} 

unordered_map<string, int> umap;

for (auto x : umap) 
	cout << x.first << " " << x.second << endl;

#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;
}

// C++ program makes a map to iterate 
// elements in reverse order with simpler 
// syntax 
#include <bits/stdc++.h> 
using namespace std; 
  
int main() 
{ 
    // Creating & Initializing a map of String & Ints 
    map<int, string> mymap; 
  
    // Inserting the elements one by one 
    mymap.insert(make_pair(10, "geeks")); 
    mymap.insert(make_pair(20, "practice")); 
    mymap.insert(make_pair(5, "contribute")); 
  
    // rbegin() returns to the last value of map 
    for (auto it = mymap.rbegin(); it != mymap.rend(); it++) { 
        cout << "(" << it->first << ", " 
             << it->second << ")" << endl; 
    } 
  
    return 0; 
}