问题

对于一个字符串S，求S的循环的同构字符串S’中字典序最小的一个。

我们举例说明，字符串”abcd”的循环同构字符串有：["abcd", "bcda", "cdab", "dabc"]。

题目的目标是 …

Introduction

There are a lot of interview problem based on the 1D-array, which is the one of the easiest “data structure”.

But the problem about that simple data structure might not be that simple. Here is the summary of the problem about 1D-array.

Of course, most of them come from …

题意

给你一个n * m的矩阵，让你做K次操作，使得最后得到的值最大。

操作有两种：

一是在任意一行上操作，最终的结果值加上这一行数的 …

443A - Anton and Letters

Simple and easy, solved by two lines of python code.

ls = filter(lambda y: y, map(lambda x: x.strip(), raw_input()[1:-1].split(",")))
print len(set(ls))

443B - Kolya and Tandem Repeat

Brute force. Just enumerate the beginning and the end of the substring, and …

Background

This problem is from the book “Algorithm 4th edition” (Exersise 4.1.10)

There are N cities and M undirected roads between those cities. People can travel to any city along the roads.

One day, a war breaks out. Our cities are under attack! As we can’t defend …

A. Squats

Trun x => X or X => x to make the number of ‘x’ is equal to the number of ‘X’.

n = int(raw_input())
hamsters = [c for c in raw_input()]

sits = hamsters.count('x')
stands = hamsters.count('X')

if sits == stands:
    print 0
    print ''.join(hamsters)
else:
    if sits > stands …

Overview

It has been months that I didn’t participate in the contest on CF, now I’m back. :)

This round of contest makes me confused that the problem B and C is a little bit too twisted, if you can’t catch the vital point, you will get a …

由于大号已经进Div. 1了，所以接下来的几场Div. 2都是用小号做的。

等有实力切D题了，再去打一区。（弱

事情一直很多，所以题解落后了好久才发。

A. Sereja …

概念

交错路

交错路：设P是图G的一条路，如果P的任意两条相邻的边一定是一条属于M而另一条不属于M，就称P是一条交错路。

通俗点来说，就是把一个图中的路径染成红黑两种。然后找出一条路，使这条路红黑 …

啥？

Tic-tac-toe是我很久之前在CF上做的一道题。非常考细心的模拟题。

最近有同学和我讨论过类似的问题。于是拿出来重新做一遍。练练手。

原题做 …