ABC 137 screencast
Problem C: I forget a hashtable whenever I use C++. C++'s hashtable is really dangerous because it doesn't use randomness.
Problem D: Considering reversed time, the items we can choose increases. Therefore, we can solve it greediliy.
Problem E: Since the problem statements says you should use Bellman-Ford, I solved it speedily. However, I mistook the way to detect positive cycles. I thought by 2N iterations the effect of positive cycles propagates to the terminal.
Problem F: Just use Lagrange's interpolation. It is difficult for me to implement division and Lagrange's interpolation. Both of them are rarely appears in contests, so that is natural. But I hope to implement them more rapidly.
