I couldn't solve this problem from Codechef Long Challenge https://www.codechef.com/OCT20A/problems/DDIMMST . Can someone help me in this problem. I tried reading the editorial https://discuss.codechef.com/t/ddimmst-editorial/79385 but no help . What i don't understand is how are we able to reduce the number of edges from n^2 to 2^d*n .

This seems to be general class of problems , there is another problem that uses the same idea https://codeforces.net/contest/1093/problem/G , awoo i know this contest was long back , can you pls explain the idea behind the solution to these kind of problems.