std::distance

std::d.cpp

#include <iostream>
#include <vector>

int main ()
{
    std::vector <int> vec = {22, 33, 2, 1, 2, 5};
    int i = 2;

    for (std::vector <int>::iterator it = vec.begin(); it != vec.end(); ++it) {
        if (*it == i ) {
            std::cout << i  << " was found at element " << std::distance(vec.begin(), it) << std::endl;
            break;
        }

    }

    return 0;
}