Want to see if any value in one vector matches the value in another vector

I am writing code for a game called Bulls & Cows. I have already solved seeing if the value of one vector (if they are in the same index) are identical. However, I am not sure how to write a for loop that will move through two vectors and see if any value in one matches the value of any other index in the other vector. I would appreciate any help. Thank you!