The std::min_element Algorithm From STL in C++

1. Use the std::min_element Algorithm to Find the Smallest Element in Range in C++
2. Use the std::minmax_element Algorithm to Find the Smallest Element and the Largest Element in Range

This article will explain how to use std::min_element algorithm from STL in C++.

Use the std::min_element Algorithm to Find the Smallest Element in Range in C++

STL algorithms include generic minimum/maximum searching functions that can operate on container ranges. std::min_element is one of these functions that retrieves the smallest element in the given range. The elements are compared with operator< when the comparison function is not explicitly specified. So if the container stores the user-defined objects, it must have the corresponding operator defined.

The range should satisfy the requirements of LegacyForwardIterator. The std::min_element function accepts two iterators and returns the iterator to the smallest element in the range. If the range includes multiple instances of the smallest element, the algorithm returns the iterator to the first of them. When the given range is empty, the second argument iterator is returned.

The following example shows the simple usage of std::min_element for the vector container. Notice that when we want the numeric position of the smallest element, one should utilize std::distance function to calculate it.

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

using std::cin;
using std::cout;
using std::endl;
using std::string;
using std::vector;

int main() {
  vector<string> v1 = {"ztop", "htop", "mtop", "ktop", "ptop"};
  vector<int> v2 = {111, 43, 12, 41, 34, 54, 13};

  auto ret = std::min_element(v1.begin(), v1.end());
  cout << "min_element(v1): " << std::setw(4) << *ret
       << "  at position: " << std::distance(v1.begin(), ret) << endl;

  auto ret2 = std::min_element(v2.begin(), v2.end());
  cout << "min_element(v2): " << std::setw(4) << *ret2
       << "  at position: " << std::distance(v2.begin(), ret2) << endl;

  return EXIT_SUCCESS;
}

min_element(v1): htop  at position: 1
min_element(v2):   12  at position: 2

Use the std::minmax_element Algorithm to Find the Smallest Element and the Largest Element in Range

Another powerful algorithm included in STL is std::minmax_element. It retrieves both the smallest and the greatest elements in the given range. std::minmax_element returns std::pair value storing the smallest element as the first member. Note that this algorithm returns the last element when there are multiple values qualifying for the greatest value in range. Mind that both of these algorithms also have overloads that can include the third parameter denoting the custom comparison function.

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

using std::cin;
using std::cout;
using std::endl;
using std::string;
using std::vector;

int main() {
  vector<string> v1 = {"ztop", "htop", "mtop", "ktop", "ptop"};
  vector<int> v2 = {111, 43, 12, 41, 34, 54, 13};

  auto ret3 = std::minmax_element(v1.begin(), v1.end());
  cout << "min (v1): " << std::setw(4) << *ret3.first
       << "| max (v1): " << std::setw(4) << *ret3.second << endl;

  auto ret4 = std::minmax_element(v2.begin(), v2.end());
  cout << "min (v2): " << std::setw(4) << *ret4.first
       << "| max (v2): " << std::setw(4) << *ret4.second << endl;

  return EXIT_SUCCESS;
}

Output:

min (v1): htop| max (v1): ztop
min (v2):   12| max (v2):  111