What's the FASTEST way to compare vectors in C++?

Question

What is the fastest way to see if two vectors are equal in c++?

I'm trying to find the fastest way to see if any row is equal to any column of a matrix, so element by element comparison and exiting the loop when not equal is not good enough.

Answer 1

Do not reinvent the wheel. You can use std::equal from <algorithm> .

It has the following complexity:

No applications of the corresponding predicate if InputIterator1 and InputIterator2 meet the requirements of random access iterators and last1 - first1 != last2 - first2. Otherwise, at most min(last1 - first1, last2 - first2) applications of the corresponding predicate.

That's what you were looking for.
See the documentation for further details.

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As mentioned in the comments, there is a subtle difference between operator== and std::equal : the former doesn't work if types are different (as an example, std::vector<int> and std::vector<double> ), the latter does work instead.
I tried to give the most generic solution.
If types are the same, of course operator== works like a charm, as mentioned by @Jarod42 .

Answer 2

Simply use operator == of vector:

std::vector<int> v1{1, 2, 3, 4}, v2{1, 2, 3, 4};
bool are_equal = (v1 == v2);

Answer 3

Equality operator ( == ) is overloaded in C++ Vector STL. So you can easily compare those directly like comparing two integers.

To compare row and column of a matrix as you said, use a loop and compare rows and columns directly by == .