Contributor disable seeing others’ posts

I hope you are talking about wp-admin section. If yes just place this code in your functions.php file

add_action( 'load-edit.php', 'posts_for_current_contributor' );
function posts_for_current_contributor() {
    global $user_ID;

    if ( current_user_can( 'contributor' ) ) {
       if ( ! isset( $_GET['author'] ) ) {
          wp_redirect( add_query_arg( 'author', $user_ID ) );
          exit;
       }
   }

}