C++ Algorithm max_element()

C++ Algorithm max_element() returns an iterator pointing to the element with the largest value in the range [first, last). If several elements fulfill this condition, the returned iterator points to the first of such elements.

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 max_element (ForwardIterator first, ForwardIterator last)

custom (2)    template <class ForwardIterator, class Compare>
                     ForwardIterator max_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 largest element.

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

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

Return value

It returns the larger 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.

Data Races

The object in the range [first, last) are accessed.

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 maximum 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 = max_element(begin(v), end(v));
    cout << "max element at position: " << distance(begin(v), result);
    
    return 0;
}

Output:

max element at position: 5

Example 2

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

#include <iostream> 
#include <algorithm> 
using namespace std; 
int main() 
{ 
    int v[] = { 'a', 'c', 'k', 'd', 'e', 'f', 'h' }; 
  
    // Finding the maximum value between the first and the 
    // fourth element 
  
    int* i1; 
    i1 = max_element(v, v + 4); 
  
    cout <<"Maximum value is: " <<char(*i1) << "\n"; 
    return 0; 
}

Output:

Maximum value is: k

Example 3

Let's see another simple example to find the largest 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 = max_element(v + 2, v + 9, comp); 
  
    cout << "Maximum element is: "<<*i1 << "\n"; 
    return 0; 
}

Output:

Maximum element is: 12

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[] = {10, 20, 30, 50, 40, 100, 70, 60, 80, 90};
    vector <int> v(arr, arr + sizeof(arr)/sizeof(int));
    map <string, int> marks;
    pair <string, int> max;
    marks["Nikita"] = 60;
    marks["Amita"] = 99;
    marks["Kashish"] = 90;
    marks["Divya"] = 80;
 
    cout << "max_element() without predicate " << endl;
    cout << "Vector : ";
    print(v);
    cout << "Maximum element = "
              << *max_element(v.begin(), v.end())
              << endl;
    cout << "\nmax_element() with predicate" << endl;
    cout << "Name\tMarks" << endl; 
    for_each(marks.begin(), marks.end(), fun);
    max = (*max_element(marks.begin(), marks.end(), compare));
    cout << "Person with maximum marks = " << max.first
              << ", Marks = " << max.second << endl;
              
    return 0;
}

Output:

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

max_element() with predicate
Name	Marks
Amita	99
Divya	80
Kashish 90
Nikita	60
Person with maximum marks = Amita, Marks = 99

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