Set and Multiset related Concepts

#1

We know generally that Sets are unordered collection of unique/distinct elements, then why are the elements in set and Multiset of C++ always ordered in ascending order?
Is it always like this? Why?

#2

No, there is unordered_set also, whose elements are not sorted. But why to use set when you can use array or vector for that purpose too. Set is created so that it will be easier for the programming to find unique elements in a certain order.

Now talking about unordered set. Its can be used as in the example below

// C++ program to demonstrate various function of unordered_set 
#include <bits/stdc++.h> 
using namespace std; 
  
int main() 
{ 
    // declaring set for storing string data-type 
    unordered_set <string> stringSet ; 
  
    // inserting various string, same string will be stored 
    // once in set 
  
    stringSet.insert("code") ; 
    stringSet.insert("in") ; 
    stringSet.insert("c++") ; 
    stringSet.insert("is") ; 
    stringSet.insert("fast") ; 
  
    string key = "slow" ; 
  
    //  find returns end iterator if key is not found, 
    //  else it returns iterator to that key 
  
    if (stringSet.find(key) == stringSet.end()) 
        cout << key << " not found" << endl << endl ; 
    else
        cout << "Found " << key << endl << endl ; 
  
    key = "c++"; 
    if (stringSet.find(key) == stringSet.end()) 
        cout << key << " not found\n" ; 
    else
        cout << "Found " << key << endl ; 
  
    // now iterating over whole set and printing its 
    // content 
    cout << "\nAll elements : "; 
    unordered_set<string> :: iterator itr; 
    for (itr = stringSet.begin(); itr != stringSet.end(); itr++) 
        cout << (*itr) << endl; 
}

output:

slow not found

Found c++

All elements : 
is
fast
c++
in
code

if you think i cleared your doubt, you can mark this as resolved. Thanks😊

#3

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