C++ Algorithm min_element()

C++ Algorithm min_element() returns an iterator pointing to the element with the smallest value in the range [first, last).

Elements are compared using operator< for the first version or using the given binary comparison function comp for the second version.

Syntax

default (1)     template <class ForwardIterator>
                       ForwardIterator min_element (ForwardIterator first, ForwardIterator last);

custom (2)      template <class ForwardIterator, class Compare>
                         ForwardIterator min_element (ForwardIterator first, ForwardIterator last,
                                                                       Compare comp);

Parameter

first: An input iterator pointing the position to the first element in the range to be searched for the smallest element.

last: An input iterator pointing the position to the past last element in the range to be searched for the smallest element.

comp: A user-defined binary predicate function that accepts two arguments and returns true if the two arguments are in order and false otherwise. It follows the strict weak ordering to order the elements.

Return value

It returns the smaller value in the range [first, last) or last if the range is empty.

Complexity

Complexity is linear in one less than the number of elements compared.

Exceptions

This function throws an exception if any comparison throws an exception.

Please note that invalid parameters cause an undefined behavior.

Example 1

Let's see the simple example to find the position of smallest element in the range:

#include <algorithm>
#include <iostream>
#include <vector>

using namespace std;

int main()
{
    vector<int> v{3, 2, 4, 1, 5, 9};
 
    vector<int>::iterator result = min_element(begin(v), end(v));
    cout << "min element at: " << distance(begin(v), result);
    
    return 0;
}

Output:

min element at: 3

Example 2

Let's see another simple example to find the smallest element in the range using default version:

#include <iostream> 
#include <algorithm> 
using namespace std; 
int main() 
{ 
    int v[] = { 9, 4, 7, 2, 5, 10, 11, 12, 1, 3, 6 }; 
  
    // Finding the minimum value between the third and the 
    // fifth element 
  
    int* i1; 
    i1 = min_element(v + 2, v + 5); 
  
    cout <<"Minimum element is: " <<*i1 << "\n"; 
    return 0; 
}

Output:

Minimum element is: 2

Example 3

Let's see another simple example to find the smallest element in the range using comparison function:

#include <iostream> 
#include <algorithm> 
using namespace std; 
  
// Defining the BinaryFunction 
bool comp(int a, int b) 
{ 
    return (a < b); 
} 
  
int main() 
{ 
    int v[] = { 9, 4, 7, 2, 5, 10, 11, 12, 1, 3, 6 }; 
  
    // Finding the minimum value between the third and the 
    // ninth element 
  
    int* i1; 
    i1 = min_element(v + 2, v + 9, comp); 
  
    cout << "Smallest element is: "<<*i1 << "\n"; 
    return 0; 
}

Output:

Smallest element is: 1

Example 4

Let's see another simple example:

#include <iostream>
#include <algorithm>
#include <vector>
#include <map>
#include <string>

using namespace std;
 
bool compare(pair<string, int> p, pair<string, int> q )
{
    return p.second < q.second;
}
 
void print(const vector <int>& v)
{
    vector <int>::const_iterator i;
    for(i = v.begin(); i != v.end(); i++)
    {
        cout << *i << " ";
    }
     cout << endl;
}
 
void fun(pair<string, int> p)
{
    cout << p.first << "\t" << p.second << endl;
}
 
int main()
{
    int arr[] = {40, 80, 50, 30, 10, 70, 60, 100, 20, 90};
    vector <int> v(arr, arr + sizeof(arr)/sizeof(int));
    map <string, int> rank;
    pair <string, int> min;
    rank["Nikita"] = 10;
    rank["Deep"] = 5;
    rank["Soonu"] = 2;
    rank["Ajeet"] = 7;
 
    cout << "min_element() without predicate " << endl;
    cout << "Vector : ";
    print(v);
    cout << "Minimum element = "
              << *min_element(v.begin(), v.end())
              << endl;
    cout << "\nmin_element() with predicate" << endl;
    cout << "Name\tMarks" << endl; 
    for_each(rank.begin(), rank.end(), fun);
    min = (*min_element(rank.begin(), rank.end(), compare));
    cout << "Person with best rank = " << min.first
              << ", Rank = " << min.second << endl;
}

Output:

min_element() without predicate 
Vector : 40 80 50 30 10 70 60 100 20 90 
Minimum element = 10

min_element() with predicate
Name	Marks
Ajeet	7
Deep	5
Nikita	10
Soonu	2
Person with best rank = Soonu, Rank = 2

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