摘要： 转载了一篇关于全排列的哈希函数，Poj1077就是应用了全排列的哈希；我们经常使用的数的进制为“常数进制”，即始终逢p进1。例如，p进制数K可表示为K = a0*p^0 + a1*p^1 + a2*p^2 + ... + an*p^n （其中0 pi，那么，如果在排列Q中qi之前的元素x与qi构成逆序对，即有x > qi，则在排列P中pi之前也有相同元素x > pi（因为x > qi且qi > pi），即在排列P中pi之前的元素x也与pi构成逆序对，所以pi的逆序数大于等于qi的逆序数。又qi与pi在排列P中构成pi的逆序对，所以pi的逆序数大于qi的逆序数。（2）同理 阅读全文

摘要： Time Limit:1000MSMemory Limit:65536KTotal Submissions:22207Accepted:9846Special JudgeDescriptionThe 15-puzzle has been around for over 100 years; even if you don't know it by that name, you've seen it. It is constructed with 15 sliding tiles, each with a number from 1 to 15 on it, and all pa 阅读全文