随笔分类 -  哈希

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

摘要：Time Limit:3500MSMemory Limit:65536KTotal Submissions:14328Accepted:5393DescriptionA square is a 4-sided polygon whose sides have equal length and adjacent sides form 90-degree angles. It is also a polygon such that rotating about its centre by 90 degrees gives the same polygon. It is not the only p 阅读全文

摘要：Time Limit:2000MSMemory Limit:65536KTotal Submissions:10711Accepted:3182DescriptionFarmer John'sNcows (1 ≤N≤ 100,000) share many similarities. In fact, FJ has been able to narrow down the list of features shared by his cows to a list of onlyKdifferent features (1 ≤K≤ 30). For example, cows exhib 阅读全文

摘要：Time Limit:4000MSMemory Limit:65536KTotal Submissions:27277Accepted:7197DescriptionYou may have heard that no two snowflakes are alike. Your task is to write a program to determine whether this is really true. Your program will read information about a collection of snowflakes, and search for a pair 阅读全文

摘要：Time Limit:5000MSMemory Limit:65536KTotal Submissions:10695Accepted:5185DescriptionConsider equations having the following form:a1x13+ a2x23+ a3x33+ a4x43+ a5x53=0The coefficients are given integers from the interval [-50,50].It is consider a solution a system (x1, x2, x3, x4, x5) that verifies the 阅读全文