做这道题,很有感悟,发篇文. 先给数列从小到大排个序. 接下来设 \(f_{i,j}\) 表示前 \(i\) 个数的排列形成 \(j\) 个上坡的方案数. 接下来考虑转移,分为插入第 \(i\) 个数后增加上坡和不增加上坡两种情况. 对于不增加的情况,有三种可能: 第 \(i\) 个数插入在了数列的最前端,有 \(1\) 种方案. 第 \(i\) 个数插入在了一个上坡的中间,因为上坡中较小的那个数字必定小于第 \(i\) 个数,形成一个上坡,较大的那个数字必定小于等于第 \(i\) 个数,不形成…

Using MLLib in ScalaFollowing code snippets can be executed in spark-shell. Binary ClassificationThe following code snippet illustrates how to load a sample dataset, execute a training algorithm on this training data using a static method in the algo…

Understanding the Bias-Variance Tradeoff When we discuss prediction models, prediction errors can be decomposed into two main subcomponents we care about: error due to "bias" and error due to "variance". There is a tradeoff between a m…

Description Professor Ibrahim has prepared the final homework for his algorithm’s class. He asked his students to implement the Posterization Image Filter. Their algorithm will be tested on an array of integers, where the i-th integer represents the…

Django-Model操作数据库(增删改查.连表结构) 一.数据库操作 1.创建model表        …

Given a non-negative integer num represented as a string, remove k digits from the number so that the new number is the smallest possible. Note: The length of num is less than 10002 and will be ≥ k. The given num does not contain any leading zero. Ex…

Given an unsorted array return whether an increasing subsequence of length 3 exists or not in the array. Formally the function should: Return true if there exists i, j, k such that arr[i] < arr[j] < arr[k] given 0 ≤ i < j < k ≤ n-1 else return…

Given an integer matrix, find the length of the longest increasing path. From each cell, you can either move to four directions: left, right, up or down. You may NOT move diagonally or move outside of the boundary (i.e. wrap-around is not allowed). E…

1. Description Given an unsorted array return whether an increasing subsequence of length 3 exists or not in the array. Formally the function should: Return true if there exists i, j, k such that arr[i] < arr[j] < arr[k] given 0 ≤ i < j < k ≤…

Buy Tickets Time Limit: 4000MS   Memory Limit: 65536K Total Submissions: 19012   Accepted: 9442 Description Railway tickets were difficult to buy around the Lunar New Year in China, so we must get up early and join a long queue… The Lunar New Year wa…