「CodeForces 1215E」 Marbles

Monocarp has arranged 𝑛 colored marbles in a row. The color of the 𝑖-th marble is 𝑎𝑖. Monocarp likes ordered things, so he wants to rearrange marbles in such a way that all marbles of the same color form a contiguos segment (and there is only one such segment for each color).

In other words, Monocarp wants to rearrange marbles so that, for every color 𝑗, if the leftmost marble of color 𝑗 is 𝑙-th in the row, and the rightmost marble of this color has position 𝑟 in the row, then every marble from 𝑙 to 𝑟 has color 𝑗.

To achieve his goal, Monocarp can do the following operation any number of times: choose two neighbouring marbles, and swap them.

You have to calculate the minimum number of operations Monocarp has to perform to rearrange the marbles. Note that the order of segments of marbles having equal color does not matter, it is only required that, for every color, all the marbles of this color form exactly one contiguous segment.

「CodeForces 1220E」 Tourism

Alex decided to go on a touristic trip over the country.

For simplicity let's assume that the country has 𝑛 cities and 𝑚 bidirectional roads connecting them. Alex lives in city 𝑠 and initially located in it. To compare different cities Alex assigned each city a score 𝑤𝑖 which is as high as interesting city seems to Alex.

「CodeForces 1241F」Stack Exterminable Arrays

Let's look at the following process: initially you have an empty stack and an array 𝑠 of the length 𝑙. You are trying to push array elements to the stack in the order 𝑠1,𝑠2,𝑠3,…𝑠𝑙. Moreover, if the stack is empty or the element at the top of this stack is not equal to the current element, then you just push the current element to the top of the stack. Otherwise, you don't push the current element to the stack and, moreover, pop the top element of the stack.

「CodeForces 1241D」Sequence Sorting

You are given a sequence 𝑎1,𝑎2,…,𝑎𝑛, consisting of integers.

You can apply the following operation to this sequence: choose some integer 𝑥 and move all elements equal to 𝑥 either to the beginning, or to the end of 𝑎. Note that you have to move all these elements in one direction in one operation.

「CodeForces1278D&E」Segment Tree & Tests for problem D

As the name of the task implies, you are asked to do some work with segments and trees.

Recall that a tree is a connected undirected graph such that there is exactly one simple path between every pair of its vertices.

You are given 𝑛 segments [𝑙1,𝑟1],[𝑙2,𝑟2],…,[𝑙𝑛,𝑟𝑛], 𝑙𝑖<𝑟𝑖 for every 𝑖. It is guaranteed that all segments' endpoints are integers, and all endpoints are unique — there is no pair of segments such that they start in the same point, end in the same point or one starts in the same point the other one ends.

「SCOI2010」股票交易

最近 lxhgww 又迷上了投资股票,通过一段时间的观察和学习,他总结出了股票行情的一些规律。

通过一段时间的观察,lxhgww 预测到了未来 T 天内某只股票的走势,第 i 天的股票买入价为每股 AP_i,第 ii 天的股票卖出价为每股 BP_i(数据保证对于每个 i,都有 APiBPiAP_i \geq BP_i,但是每天不能无限制地交易,于是股票交易所规定第 i 天的一次买入至多只能购买 AS_i股,一次卖出至多只能卖出 BS_i股。

另外,股票交易所还制定了两个规定。为了避免大家疯狂交易,股票交易所规定在两次交易(某一天的买入或者卖出均算是一次交易)之间,至少要间隔 WW 天,也就是说如果在第 ii 天发生了交易,那么从第 i+1 天到第 i+W 天,均不能发生交易。同时,为了避免垄断,股票交易所还规定在任何时间,一个人的手里的股票数不能超过 MaxP。

在第 1 天之前,lxhgww 手里有一大笔钱(可以认为钱的数目无限),但是没有任何股票,当然,T 天以后,lxhgww 想要赚到最多的钱,聪明的程序员们,你们能帮助他吗?

「SDOI2009」学校食堂

小F 的学校在城市的一个偏僻角落,所有学生都只好在学校吃饭。学校有一个食堂,虽然简陋,但食堂大厨总能做出让同学们满意的菜肴。当然,不同的人口味也不一定相同,但每个人的口味都可以用一个非负整数表示。 由于人手不够,食堂每次只能为一个人做菜。做每道菜所需的时间是和前一道菜有关的,若前一道菜的对应的口味是a,这一道为b,则做这道菜所需的时间为(a or b)-(a and b),而做第一道菜是不需要计算时间的。其中,or 和and 表示整数逐位或运算及逐位与运算,C语言中对应的运算符为“|”和“&”。

「CodeForces 1254B」Send Boxes to Alice

This is the harder version of the problem. In this version, 1≤𝑛≤106 and 0≤𝑎𝑖≤106. You can hack this problem if you locked it. But you can hack the previous problem only if you locked both problems

Christmas is coming, and our protagonist, Bob, is preparing a spectacular present for his long-time best friend Alice. This year, he decides to prepare 𝑛 boxes of chocolate, numbered from 1 to 𝑛. Initially, the 𝑖-th box contains 𝑎𝑖 chocolate pieces.

「CodeForces 1277E」 Two Fairs

There are 𝑛 cities in Berland and some pairs of them are connected by two-way roads. It is guaranteed that you can pass from any city to any other, moving along the roads. Cities are numerated from 1 to 𝑛.

Two fairs are currently taking place in Berland — they are held in two different cities 𝑎 and 𝑏 (1≤𝑎,𝑏≤𝑛; 𝑎≠𝑏).