Set Find Function in C++ Programming STL

In this article we are going to discuss the set::find() function in C++ STL, their syntax, working and their return values.

What is Set in C++ STL?

Sets in C++ STL are the containers which must have unique elements in a general order. Sets must have unique elements because the value of the element identifies the element. Once added a value in a set container later can't be modified, although we can still remove or add the values to the set. Sets are used as binary search trees.

What is set::find()

The std::find() function is an inbuilt function in C++ STL, which is defined in header file. This function is used to find an element or a value in a set container. find() returns an iterator which points to the position of the element which is searched. If the element is not present in the set, then it returns the element just after the last element of the set container.

Syntax

Following is the syntax is as follows:

Set1.find(const type_t& element);

Parameter

This function accepts one parameter, i.e., element which is to be found.

Return value

This function returns an iterator which points to the element which is to be found.

Example Scenario

Following is the example for Input and Output Scenario:

Input: set<int> 
myset = {10, 20, 40, 80, 90};
myset.find(40);
Output: element found

Let us go through the program examples for better understanding.

Example 1: Find a Value using std::set

In this example, we use std::find() function to locate the value 40 in a set and then iterates from that point to print all elements to the end.

#include <bits/stdc++.h>
using namespace std;
int main(){
   set<int> mySet;
   mySet.insert(10);
   mySet.insert(20);
   mySet.insert(90);
   mySet.insert(80);
   mySet.insert(40);
   auto temp = mySet.find(40);
   cout<<"Elements after 40 are: ";
   for (auto i = temp; i != mySet.end(); i++)
      cout << *i << " ";
   return 0;
}

If we run the above code then it will generate the following output:

Elements after 40 are: 40 80 90

Example 2: Remove elements from std::set Using find() and erase()

In this example, we demonstrate how to remove specific elements from a set using find() to locate and erase() to delete them.

#include <iostream>
#include <set>
int main (){
   std::set<int> mySet;
   std::set<int>::iterator i;
   for(int i=1; i<=4; i++)
      mySet.insert(i*2);
   i = mySet.find(6);
   mySet.erase(i);
   mySet.erase(mySet.find(4));
   std::cout<<"elements are : ";
   for (i = mySet.begin(); i != mySet.end(); ++i)
      std::cout << ' ' << *i;
   std::cout << '\n';
   return 0;
}

If we run the above code then it will generate the following output:

Elements are : 2 8