题目描述Vasily has a deck of cards consisting of $n$ cards. There is an integer on each of the cards, this integer is between $1$ and $100000$, inclusive. It is possible that some cards have the same inte

题目描述There are $n$ people and $k$ keys on a straight line. Every person wants to get to the office which is located on the line as well. To do that, he needs to reach some point with a key, take the ke

题目描述Everyone knows that DNA strands consist of nucleotides. There are four types of nucleotides: “A”, “T”, “G”, “C”. A DNA strand is a sequence of nucleotides. Scientists decided to track evolution of

题目描述Ivan had string $s$ consisting of small English letters. However, his friend Julia decided to make fun of him and hid the string $s$. Ivan preferred making a new string to finding the old one. Iva

题意概述有$n$个排成一行的传送器，第$i$个传送器可以传送到$[L_i, R_i]$之间的所有传送器上（传送前的身影还在），可以多次传送。你现在随机出生在一个传送器上，求有你身影的传送器个数的期望。 算法分析首先利用线段树优化建图，使得点数为$O(n)$，边数为$O(n\log n)$。 这是一张有向图。考虑在同一个强连通分量中的两个点，它们的答案一定是一样的。因此可以将图中的强连通分量缩成一个

题目描述Arkady needs your help again! This time he decided to build his own high-speed Internet exchange point. It should consist of $n$ nodes connected with minimum possible number of wires into one netw

题目描述Chef has a calculator which has two screens and two buttons. Initially, each screen shows the number zero. Pressing the first button increments the number on the first screen by $1$, and each clic

题目描述Chef found a strange string yesterday - a string of signs $s$, where each sign is either a ‘<’, ‘=’ or a ‘>’. Let $N$ be the length of this string. Chef wants to insert $N+1$ positive i

题目描述Rick and Morty want to find MR. PBH and they can’t do it alone. So they need of Mr. Meeseeks. They Have generated $n$ Mr. Meeseeks, standing in a line numbered from $1$ to $n$. Each of them has hi

题目描述A little boy Pishty lives in Khust - an ancient town in Uzhlyandia with their medieval castles and smart bears. The gem of Khust is a very valuable castle because it protects the citizens of Uhzly