Is there any solution that will merge two sets in n=( size_of_se1 + size_of_set2 ) times in c++? If I iterate through both the sets and take the smaller value and insert it in another set, this way I can merge two sets but it will take close to n*logn time as set insert operation takes logn time. Also I can let the set1 unchanged and insert all the elements of set2 in set1 or vice versa but it will also take size_of_set2*log(size_of_set1) or size_of_set1*log(size_of_set2) time. I am searching for a solution if it is actually possible to merge two sets in linear time. I googled it and spend some time to find out any solution regarding to it but failed :( Can anyone help me with your valuable opinion? thanks in advance :)

Is it possible to use a structure as the key of a map?! If it is, then how can I do this? thanks in advance.

It will be very great if Codeforces open a new section where there will be a platform to disscuss about different algorithm wise topics... there will be many different sector where different algorihm based questions will be solved... Suppose any one need any help about any algorithm related to graph theory, then he/she can ask question on graph theory section(there will be many sections like grap theory), if this topic is discussed earlier then codefrces will provide him/her information related to this question otherwise anybody who know well about this question will share his/her knowledge about the question and this information also be saved for future use as this question is new. By this we all can able to learn and share our knowledge thus can develop our skill in programming. This will provide us instant solution of any confusion about any algorithm wise problem.

What is the problem of rating change of todays contest?! Why the rating is changing sevaral times?! Can the authority give us some message?!