Atcoder ABC 412 скачать в хорошем качестве

Atcoder ABC 412

I participated in AtCoder ABC 412 and solved problems A–F. problem F: https://atcoder.jp/contests/abc412/ta... Given N sock types (N ≤ 200,000, each ≤ 3,000 socks), you repeatedly draw and return one sock until you draw a sock matching the one in your hand (in which case you stop and don’t return it). The challenge is to find the expected number of draws, playing optimally. The key is always returning the most frequent sock type. This leads to a DP over sock counts: dp[c] = expected draws when holding a sock of count c, with transitions weighted by the distribution of sock types.