This is a hard version of Ep. 67. If you prefer an easier problem, please see OBCYSIO67. Meeting Point Given a directed graph G of n vertices and m edges. A single vertex S is called the starting point and a single vertex T is called the finish poi……

Solved! Difficulty: D2C Pretty basic exercise problem from FLA This is an easy version of Ep. 68. If you prefer harder problems, please visit here. Meeting Point Given a directed graph G of n vertices and m edges. A single vertex S is called ……

Solved! Difficulty: Div2C Classic 思考题 HP You are given a grid of n*m cells. You start from a starting cell S and can move up, down, left or right in one step without leaving the grid. Find: is it possible to visit each cell once and exactl……

Solved Difficulty: D2C 思考题 inspired by Saionji Video Channel Eastmost Eki There are n points on a 2D plane. You can select any real point as pivot in the rectangle bounded by (a,b) and (c,d) and rotate the entire plane by d degree clockwis……

思考题 inspired by car lanes Car Lane In Ryuto the capital of the Dragon Kingdom, there is an intersection with k+1 exits. On one lane of one exit, there is a queue of n cars. The i-th car in the queue wants to go in the direction d_i (1\leq d_i\le……

Solved Difficulty: D2C-D2D 思考题 inspired by Create Mod Assembly Line There is an assembly line consisting of n machines. The i-th machine on the line holds an infinitely long input queue and a processing time of t_i seconds. The machines wo……

short 思考题 A^B Problem Given two pattern strings A and B that consists of lower-case letters, ? (match a single character) and * (match zero or more characters) For example, abc?d*e matches abcfdppe and abcgde but not ae or abcdee. Find a string ……

思考题 featuring Hikari again! Guess the string Hikari and her master Ninetail are playing a game. Hikari thinks of a string S with lower-case letters, and Ninetail asks her to make q modifications one by one. Each modification can only be one of t……

思考题 from Maths homework again... Why 60.5? Not because it has sth to do with the previous problem, which happens to also be a math problem. It's because the next OBCYSIO was also named as Ep.61 and the problem was discovered 1 year later!! 数学……

Solved! Difficulty: Div2C :O 竟然有60期了！！ 本期题目来源于Group Theory作业，，，难度不高 Congratulations on the 60th entry!! This problem is from my Group Theory homework (not very hard). Z(Sym(n))=ONE In the world of MATHS, a permutation i……