摘要：原题 Roman planted a tree consisting of n vertices. Each vertex contains a lowercase English letter. Vertex 1 is the root of the tree, each of the n - 1 阅读全文

摘要：原题 Given a sequence of n numbers a1, a2, ..., an and a number of d-queries. A d-query is a pair (i, j) (1 ≤ i ≤ j ≤ n). For each d-query (i, j), you h 阅读全文

摘要：原题 题目描述 Z 国的骑士团是一个很有势力的组织，帮会中汇聚了来自各地的精英。他们劫富济贫，惩恶扬善，受到社会各界的赞扬。 最近发生了一件可怕的事情，邪恶的 Y 国发动了一场针对 Z 国的侵略战争。战火绵延五百里，在和平环境中安逸了数百年的 Z 国又怎能抵挡的住 Y 国的军队。于是人们把所有的希望 阅读全文

摘要：原题 Once Petya read a problem about a bracket sequence. He gave it much thought but didn't find a solution. Today you will face it. You are given strin 阅读全文