分类： ACM

For Argo, it is very interesting watching a circle bouncing in a rectangle.

As shown in the figure below, the rectangle is divided into N×M grids, and the circle fits exactly one grid.

The bouncing rule is simple:

1. The circle always starts from the left upper corner and moves towards lower right.

2. If the circle touches any edge of the rectangle, it will bounce.

3. If the circle reaches any corner of the rectangle after starting, it will stop there.

Argo wants to know how many grids the circle will go through only once until it first reaches another corner. Can you help him?
继续阅读“2017ICPC北京网络赛 G | hihocoder 1584 Bounce”

描述

There is a strong data structure called “Suffix Array” which can effectively solve string problems.

Let S=s₁s₂…s_n be a string and let S[i,j] denote the substring of S ranging from i to j. The suffix array A of S is now defined to be an array of integers providing the starting positions of suffixes of S in lexicographical order. This means, an entry A[i] is the starting position of the i-th smallest suffix in S and thus for all 1 < i ≤ n:  S[A[i-1], n] < S[A[i], n].

For example: the suffix array of “banana” is [6, 4, 2, 1, 5, 3].

Here comes another problem called “Reverse Suffix Array”.

Given a suffix array, you need to figure out how many lower case strings are there whose suffix array is the same as the given suffix array.
继续阅读“2017ICPC北京网络赛 B | hihocoder 1579 Reverse Suffix Array”