i wanted to know, why there is no king in UK.
As King was there during Golden Revolution, and some of Europe states have king as a Head of state.
CAn anyone explain me why not same in UK
The reason there is not (currently) a King in the United Kingdom, is because the eldest child and Heir of Blood Royal of the previous Sovereign, King George V, was female, the then HRH Princess Elizabeth. After the death of King George V, since there were no male heirs in direct succession, the eldest female in direct succession ascended to the throne.
Now with the current situation, the current heir apparent to the throne is Prine Charles of Wales (Lord of the Isles, Duke of Cornwall, and the other customary titles for the heir to the Crown). Additionally, Prince Charles has two sons, the Princes William and Harry, all of whom are in a line of direct succession. Prince Charles also has several brothers to whom the Crown could pass due, in the event of a series of deaths and/or abdications.
As a side note, from what I recall, there was supposed to have been a stipulation of the divorce agreement between Prince Charles and Princess Diana where the Crown would pass directly to Prince William upon the death of incapacity of Queen Elizabeth II. I admit however, that was someone I remember reading prior to the death of Princess Diana, so it has been some time and my recollection could be faulty.
-Cheers