# acm

# POJ3020

POJ3020 Antenna Placement Time Limit: 1000MS Memory Limit: 65536K Total Submissions: 10821 Accepted: 5324 Description The Global Aerial Research Centre has been allotted the task of building the fifth generation of mobile phone nets in Sweden. The most striking reason why they got the job, is their discovery of a new, highly noise resistant, antenna. It is called 4DAir, and comes in four types. Each type can only transmit and receive signals in a direction aligned with a (slightly skewed) latitudinal and longitudinal grid, because of the interacting electromagnetic field of the earth. The four types correspond to antennas operating in the directions north, west, south, and east, respectively. Below is an example picture of places of interest, depicted by twelve small rings, and nine 4DAir antennas depicted by ellipses covering them.

# Codeforces #733 D

733D D. Kostya the Sculptor time limit per test 3 seconds memory limit per test 256 megabytes input standard input output standard output Kostya is a genial sculptor, he has an idea: to carve a marble sculpture in the shape of a sphere. Kostya has a friend Zahar who works at a career. Zahar knows about Kostya’s idea and wants to present him a rectangular parallelepiped of marble from which he can carve the sphere.

# Codeforces #719 C

719C C. Efim and Strange Grade time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output

# POJ1458

POJ1458 Common Subsequence Time Limit: 1000MS Memory Limit: 10000K Total Submissions: 44778 Accepted: 18346 Description A subsequence of a given sequence is the given sequence with some elements (possible none) left out. Given a sequence X = < x1, x2, …, xm > another sequence Z = < z1, z2, …, zk > is a subsequence of X if there exists a strictly increasing sequence < i1, i2, …, ik > of indices of X such that for all j = 1,2,…,k, xij = zj. For example, Z = < a, b, f, c > is a subsequence of X = < a, b, c, f, b, c > with index sequence < 1, 2, 4, 6 >. Given two sequences X and Y the problem is to find the length of the maximum-length common subsequence of X and Y.

# POJ1961

POJ1961 Period Time Limit: 3000MS Memory Limit: 30000K Total Submissions: 15006 Accepted: 7158 Description For each prefix of a given string S with N characters (each character has an ASCII code between 97 and 126, inclusive), we want to know whether the prefix is a periodic string. That is, for each i (2 <= i <= N) we want to know the largest K > 1 (if there is one) such that the prefix of S with length i can be written as AK ,that is A concatenated K times, for some string A. Of course, we also want to know the period K.

# POJ1686

POJ1686 Lazy Math Instructor Time Limit: 1000MS Memory Limit: 10000K Total Submissions: 3766 Accepted: 1307 Description A math instructor is too lazy to grade a question in the exam papers in which students are supposed to produce a complicated formula for the question asked. Students may write correct answers in different forms which makes grading very hard. So, the instructor needs help from computer programmers and you can help.