You can do yes | cp -rf xxx yyy, but my gutfeeling says that if you do it as root – your .bashrc or .profile has an alias of cp to cp -i, most modern systems (primarily RH-derivatives) do that to root profiles.
You can check existing aliases by running alias at the command prompt, or which cp to check aliases only for cp.
If you do have an alias defined, running unalias cp will abolish that for the current session, otherwise you can just remove it from your shell profile.
You can temporarily bypass an alias and use the non-aliased version of a command by prefixing it with \, e.g. \cp whatever