Segment tree

1. http://se7so.blogspot.in/2012/12/segment-trees-and-lazy-propagation.html

(the first solutin is buggy) , see the last one

list of good questions  

1.can you answer these queries (gss1) , solu -: https://github.com/VitSalis/SPOJ/blob/master/GSS1/gss1.cpp