std::find in C++

std::find is a function defined inside <algorithm> header file that finds the element in the given range. It returns an iterator to the first occurrence of the specified element in the given sequence. If the element is not found, an iterator to the end is returned.

Syntax:

input_iterator std::find(input_iterator first, input_iterator last, const T& value);

Parameters:

• first: iterator to the initial position in the sequence.
• last: iterator to the final position in the sequence.
• value: value to be searched.

Return Value :

• If the value is found in the sequence, the iterator to its position is returned.
• If the value is not found, the iterator to the last position is returned.

NOTE: input_iterator is the iterator type of the used container and T is the typename defined in the function template.

Example:

C++

// C++ program to Demonstrate
// std::find for vectors
#include <bits/stdc++.h>

// Driver code
int main()
{
  std::vector<int> vec{10, 20, 30, 40};

  // Iterator used to store the position
  // of searched element
  std::vector<int>::iterator it;

  // Print Original Vector
  std::cout << "Original vector :";

  for (int i = 0; i < vec.size(); i++)
    std::cout << " " << vec[i];

  std::cout << "\n";

  // Element to be searched
  int ser = 30;

  // std::find function call
  it = std::find(vec.begin(),
                 vec.end(), ser);
  if (it != vec.end())
  {
    std::cout << "Element " << ser <<
                 " found at position : ";
    std::cout << it - vec.begin() <<
                 " (counting from zero) \n";
  }
  else
    std::cout << "Element not found.\n\n";

  return 0;
}

Output

Original vector : 10 20 30 40
Element 30 found at position : 2 (counting from zero) 

Time Complexity: O(n)
Auxiliary Space: O(1)

NOTE: std::find() function is defined inside <algorithm> header file. So, we need to include that header file before using find function.

As we can see that the time complexity of the std::find() is O(n) and it also works on unsorted sequences, we can conclude that it uses the linear search algorithm in its implementation.

This article is contributed by Sachin Bisht. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks. Please write comments if you find anything incorrect, or if you want to share more information about the topic discussed above.