max_element in C++ STL

The std::max_element() in C++ is an STL algorithm that is used to find the maximum element in the given range. It is defined inside the <algorithm> header file. In this article, we will learn how to find the maximum element in the range using std::max_element() in C++.

Example:

// C++ program to illustrate the use of 
// std::max_element()
#include <bits/stdc++.h>
using namespace std;

int main() {
    vector<int> v = {2, 1, 17, 10};
  	int arr[4] = {33, 87, 1, 71};
  	int n = sizeof(arr)/sizeof(arr[0]);
    
  	// Max element in vector
    cout << *max_element(v.begin(), v.end()) << endl;
  
  	// Max element in array
    cout << *max_element(arr, arr + n);
  	
    return 0;
}

17
87

std::max_element() Syntax

std::max_element(first, last, comp);

Parameters

• first: Iterator to the first element of the range.
• last: Iterator to the element just after the last element of the range.
• comp: Binary comparator function, functor or lambda expression that compares two elements in the range. By default, it is set as < operator.

Return Value

• Returns an iterator to the largest element in the range.
• When the range is empty, it returns iterator to the last.

More Examples of std::max_element()

We can find the maximum element of the given range using std::max_element(). This range can be std::vector, array, list or any other container.

Example 1: Find Maximum Element in Array

// C++ program to illustrate the use of 
// std::max_element() in array
#include <bits/stdc++.h>
using namespace std;

int main() {
    int arr[] = {33, 87, 1, 71};
    int n = sizeof(arr)/sizeof(arr[0]);
  
    // Finding the maximum element in array
    cout << *max_element(arr, arr + n);
    return 0;
}

87

Time Complexity: O(n), where n is the number of elements in array.
Auxiliary Space: O(1)

Example 2: Finding Element Having Maximum Remainder After Division with 5

For this purpose, we have to use the custom comparator function.

// C++ program to illustrate the use of custom
// comparator with std::max_element()
#include <bits/stdc++.h>
using namespace std;

// Function that returns true if the first
// argument have smaller remainder left after
// division with 5
bool comp(int a, int b) {
  return a % 5 < b % 5;
}

int main() {
    vector<int> v = {33, 87, 1, 71};
  
    // Finding the maximum element in given 
    // range of vector
    cout << *max_element(v.begin(), v.end(),
                         comp);
    return 0;
}

33

Time Complexity: O(n), where n is the number of elements in vector.
Auxiliary Space: O(1)

Example 3: Find Maximum Element in Vector of User Defined Data Type

We have to use custom comparator again to determine how to compare user defined data type on any of its property.

// C++ Program to find the maximum element in 
// the vector of structure
#include <bits/stdc++.h>
using namespace std;

struct St {
    string name;
    int sno;
};

int main() {
  
    // Create a vector of structure
    vector<St> v = {{"Ashok", 11}, {"Deepak", 15}, 
                    {"Anmol", 23}, {"Vikas", 19}};

    // Find the maximum element in the vector of structure
    // based on the sno field
    St max = *max_element(v.begin(), v.end(),
                    [](const St &i, const St &j) { 
                        return i.sno < j.sno;
                    });

    cout << max.name << " " << max.sno;
    return 0;
}

Anmol 23

Time Complexity: O(n), where n is the number of elements in the vector.
Auxiliary Space: O(1)

Working of std::max_element()

std::max_element() implements linear search algorithm to find the largest element in the range. It compares each element of the range one by one using the iterator/pointer provided to it as arguments. This is the reason why it gives O(n) linear time complexity.

std::max_element() not specialized for sorted containers such as std::set, std::map, etc. and still will compare all the elements of these containers to find the maximum element.