摘要：已经写过本题用二分图的做法， "见这儿" 。 本题的图是一棵树，求最小点覆盖也可以用树形DP的做法。 定义状态f[0/1][u]表示以u为根的子树，u选取/不选最少需要选取多少点来覆盖。 显然 f[0][u] = Sigma{f[1][v]},f[1][u] = Sigma{min(f[0][v], 阅读全文

摘要：The cows, who always have an inferiority complex about their intelligence, have a new guessing game to sharpen their brains.A designated 'Hay Cow' hid 阅读全文