C++ Program to Find Member Function in Vector

In C++, the find() member function in the vector class is used to search for a specific element in a vector. It returns an iterator pointing to the first occurrence of the element if found, or the vector::end() iterator if the element is not present.

Syntax

The syntax for using the find() member function in vector is:

std::vector<T>::iterator std::find (std::vector<T>::iterator first, std::vector<T>::iterator last, const T& val);

Here, first and last are iterators that denote the range of elements to be searched, and val is the value to be searched.

Example

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

int main()
{
    std::vector<int> vec{ 10, 20, 30, 40, 50 };

    // Find 30 in the vector
    auto it = std::find(vec.begin(), vec.end(), 30);

    // If element is found, print the index
    if (it != vec.end()) {
        std::cout << "Element found at index: " << std::distance(vec.begin(), it);
    }
    else {
        std::cout << "Element not found";
    }

    return 0;
}

Output

Element found at index: 2

Explanation

In the above code, we have defined a vector containing some elements. We then used the find() member function to search for the element 30 in the vector. The function returns an iterator pointing to the first occurrence of the element, which is then compared with the vector::end() iterator to check if the element was found or not. If found, the distance between the first iterator and the found iterator is printed as the index of the element in the vector.

Use

The find() member function in vector is used to search for a specific element in the vector. It is useful when you want to check if an element is present in the vector, or to find the index of the first occurrence of the element.

Important Points

• The find() member function works only on sorted vectors.
• The find() member function returns an iterator pointing to the first occurrence of the element in the vector, or the vector::end() iterator if the element is not present.
• The function takes O(N) time as it needs to search every element in the vector.

Summary

In summary, the find() member function in vector is a powerful tool to search for a specific element in the vector. It returns an iterator to the first occurrence of the element, or the vector::end() iterator if the element is not present. While it takes linear time to perform the search, it is still an efficient way to check if an element is present in the vector or to find its index.