Thanks, for your Time.

At line 41 Use :
int cntop[maxn]={0}, cntcl[op] ={0};
Instead :
int cntop[maxn], cntcl[op] ;
rep(i,maxn) cntop[i] = cntcl[i] = 0 ;

I want to know what does it mean by saying "number of components in it is equal to a" ?
(i.e. what 'a' & 'b' refers to ?)

Can anyone explain problem D. How are we calculating the results ?

In problem D tutorial, how is k equal to L ?

Well it cover a lot of generally used Data structure, Thanks;