摘要：dlstxdy!zrtxdy! 阅读全文

摘要：比赛链接 "cf" A 最后一位判定 C 所有方案 全是红边的方案 并查集维护 cpp include include include include include include include include include using namespace std; typedef long 阅读全文

摘要：第一道容斥 $ans[i] = \sum_{j = 0}^{min(cnt, n / 2)} ( 1)^j \tbinom{cnt}{j} \tbinom{n 2 j + k 1}{k 1}$ i 为 [2, 2k] cnt是满足x, y小于等于k 且 x + y = i 的对的种类数 后面那个组合 阅读全文