utkarshl

In order to use segtree class defined above, you will need to create a datatype(a struct most likely), which will implement the function merge(). It can also additionally implement split, if you need to define the split operation.
A sample is shown as "struct segtree_node" in the code above.

The segtree has to be instantiated with this defined data type. For example,as 
segtree<segtree_node> s;

You have to first call the init function of the class, which will take 
  int n=number of elements in your array,
  node[] = your inital array,
  identity = an element such that merge(y,identity) = merge(identity,y) = y for all y's.