Problem F Funny Car Racing There is a funny car racing in a city with n junctions and m directed roads. The funny part is: each road is open and closed periodically. Each road is associate with two integers (a, b), that means the road will be open fo…

Problem A Almost Palindrome Given a line of text, find the longest almost-palindrome substring. A string S is almost-palindrome if S begins and ends with a letter, and a(S) and b(S) have at most 2k positions with different characters Here a(S) is the…

Problem H High bridge, low bridge Q: There are one high bridge and one low bridge across the river. The river has flooded twice, why the high bridge is flooded twice but the low bridge is flooded only once? A: Because the lower bridge is so low that…

Problem I Interesting Calculator There is an interesting calculator. It has 3 rows of button. Row 1: button 0, 1, 2, 3, ..., 9. Pressing each button appends that digit to the end of the display. Row 2: button +0, +1, +2, +3, ..., +9. Pressing each bu…

Problem J Joking with Fermat's Last Theorem Fermat's Last Theorem: no three positive integers a, b, and c can satisfy the equation an + bn = cn for any integer value of n greater than two. From the theorem, we know that a3 + b3 = c3 has no positive i…

Problem G Good Teacher I want to be a good teacher, so at least I need to remember all the student names. However, there are too many students, so I failed. It is a shame, so I don't want my students to know this. Whenever I need to call someone, I c…

Problem L Last Blood In many programming contests, special prizes are given to teams who solved a particular problem first. We call the first accepted solution "First Blood". It's an interesting idea to set prizes for "Last Blood". The…

Problem C Character Recognition? Write a program that recognizes characters. Don't worry, because you only need to recognize three digits: 1, 2 and 3. Here they are: .*. *** *** .*. ..* ..* .*. *** *** .*. *.. ..* .*. *** *** Input The input contains…

链接: https://codeforces.com/gym/102394/problem/F 题意: Harbin, whose name was originally a Manchu word meaning "a place for drying fishing nets", grew from a small rural settlement on the Songhua River to become one of the largest cities in Northea…

题目链接:https://codeforces.com/gym/102361/problem/F 题意 有 \(n\) 个点和 \(m\) 条边,每条边属于 \(0\) 或 \(1\) 个环,问去掉一些边使得图变为森林的方案个数. 题解 找出所有环的长度 \(c_i\),每个环可以去掉 \(1,2,\dots,c_i\) 条边,方案各为 \(C_{c_i}^1,C_{c_i}^2, \dots C_{c_i}^{c_i}\),即 \(2^{c_i} - 1\) . 所有环的去边方案共有 \(\p…