Fastest way for getting last index of item in vector in C++?

Let's say you have a vector of ints, unsorted and with multiple repeating items, like so:

vector<int> myVec{1, 0, 0, 0, 1, 1, 0, 1,0,0}

What is the fastest way to get the last index of 1 which is 8 for this example, other than looping through it from its end?

Would this be different if the vector would contain other items than 0 and 1?

What is the fastest way to do this in C++?

Thank you!