Traversing a map (or unordered_map) in C++ STL

We can traverse map and unordered_map using following different ways.

map

// CPP program to traverse a map using range  
// based for loop 
#include <bits/stdc++.h> 
using namespace std; 
  
int main() 
{ 
    int arr[] = { 1, 1, 2, 1, 1, 3, 4, 3 }; 
    int n = sizeof(arr) / sizeof(arr[0]); 
  
    map<int, int> m; 
    for (int i = 0; i < n; i++) 
        m[arr[i]]++; 
  
    cout << "Element  Frequency" << endl; 
    for (auto i : m) 
        cout << i.first << "   " << i.second  
             << endl; 
  
    return 0; 
} 

unordered_map

// CPP program to traverse a unordered_map using  
// range based for loop 
#include <bits/stdc++.h> 
using namespace std; 
  
int main() 
{ 
    int arr[] = { 1, 1, 2, 1, 1, 3, 4, 3 }; 
    int n = sizeof(arr) / sizeof(arr[0]); 
  
    unordered_map<int, int> m; 
    for (int i = 0; i < n; i++) 
        m[arr[i]]++; 
  
    cout << "Element Frequency" << endl; 
    for (auto i : m) 
        cout << i.first << "    " << i.second 
             << endl; 
  
    return 0; 
} 

Output [NOTE: For unordered_map output rows can be
in any order]

Element  Frequency
1        4
2        1
3        2
4        1

Traversing using begin() and end()

map

// CPP program to traverse a map using iterators 
#include <bits/stdc++.h> 
using namespace std; 
  
int main() 
{ 
    int arr[] = { 1, 1, 2, 1, 1, 3, 4, 3 }; 
    int n = sizeof(arr) / sizeof(arr[0]); 
  
    map<int, int> m; 
    for (int i = 0; i < n; i++) 
        m[arr[i]]++; 
  
    cout << " Element Frequency" << endl; 
    for (auto i = m.begin(); i != m.end(); i++) 
        cout << i->first << "      " << i->second 
             << endl; 
  
    return 0; 
} 

unordered_map

// CPP program to traverse a unordered_map  
// using iterators 
#include <bits/stdc++.h> 
using namespace std; 
  
int main() 
{ 
    int arr[] = { 1, 1, 2, 1, 1, 3, 4, 3 }; 
    int n = sizeof(arr) / sizeof(arr[0]); 
  
    unordered_map<int, int> m; 
    for (int i = 0; i < n; i++) 
        m[arr[i]]++; 
  
    cout << " Element Frequency" << endl; 
    for (auto i = m.begin(); i != m.end(); i++) 
        cout << i->first << "       " << i->second  
             << endl; 
  
    return 0; 
} 

Output [NOTE: For unordered_map output rows can be
in any order]

Element  Frequency
1        4
2        1
3        2
4        1

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My Personal Notes

map

unordered_map

map

unordered_map

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