Added implicit unwrapped optionals
Added implicit unwrapped optionals

hanhailong/practice-swift,hanhailong/practice-swift,domenicosolazzo/practice-swift,nguyenantinhbk77/practice-swift,domenicosolazzo/practice-swift,domenicosolazzo/practice-swift,nguyenantinhbk77/practice-swift,nguyenantinhbk77/practice-swift,hanhailong/practice-swift,nguyenantinhbk77/practice-swift,domenicosolazzo/practice-swift,hanhailong/practice-swift