Why do some programmers add rng(chrono::steady_clock::now().time_since_epoch().count()); in their template.
Also why typedef tree<int, null_type, less, rb_tree_tag, tree_order_statistics_node_update> pbds;
Can you also share me best competitive programming template you have ever seen?

Suggest some strategies to prepare for ICPC. My team is okayish and we are very close friends so communication and understanding is also good.
Are cses problems good from ICPC point of view. If not, can you suggest some other resources.
I would also love to hear about sites which allows team participation.

Given an array of size n-1 filled with elements from 1 to n with one missing number. Find that missing number using divide and conquer.
I google it and found many binary search algorithms but couldn't find any divide and conquer approach. Anybody know how to solve it.