天下之大

摘要： ZOJ Problem Set - 1201Inversion Time Limit: 1 Second Memory Limit: 32768 KB Let { A1,A2,...,An } be a permutation of the set{ 1,2,..., n}. If i < j and Ai > Aj then the pair (Ai,Aj) is called an "inversion" of the permutation. For example, the permutation {3, 1, 4, 2} has three inversions: ( 阅读全文

摘要： Parencodings Time Limit: 1 Second Memory Limit: 32768 KB Let S = s1 s2 ... s2n be a well-formed string of parentheses. S can be encoded in two different ways:By an integer sequence P = p1 p2 ... pn ... 阅读全文

摘要： 弦图是图论里面的概念。一个图被称作弦图时，它满足对于它的任意一个顶点数大于3的环，都至少有一条弦。这是ZOJ 1015中涉及的一个概念，至今无法理解。我的理解：这里提到的“环”应该是多边形的环吧，那弦就是连接不相邻节点的线段。既然划了线，那就等于把环切成两个环了，那剩下的两个环也都必须遵守这个规则吧。既然顶点大于3都要被切割，那索性全是三角形了？不知道我的理解哪里有问题，请... 阅读全文

摘要： Jugs Time Limit: 1 Second Memory Limit: 32768 KB Special Judge In the movie "Die Hard 3", Bruce Willis and Samuel L. Jackson were confronted with the following puzzle. They were given a 3-gallon jug... 阅读全文