CF351E Jeff and Permutation 贪心好题 考虑每个对能否最小化贡献和 先不考虑绝对值相同情况 发现,对于a,b假设|a|<|b|,那么有无贡献只和b的正负有关!如果a在b前面,b取负一定有贡献,a在b后面,b取正一定有贡献 所以,每个对划分给绝对值较大的管辖,管辖关系形成DAG,显然管辖之间互不影响! 一个点的贡献最小就是左边和右边绝对值比它小的个数的较小值! 对于绝对值相同的情况,我们发现这样进行赋值之后,绝对值相同的一定可以呈现出一段负之后一段正的情况 https:/…

http://codeforces.com/contest/351/problem/E 题意: 给出一些数,可以改变任意数的正负,使序列的逆序对数量最少 因为可以任意加负号,所以可以先把所有数看作正数 序列中的数无论怎么改,都不会改变与绝对值最大的数的逆序对的数量 所以从绝对值最大的数开始,决定它的正负 若这个序列中没有重复的最大值 若i是正数,与右边比他小的形成逆序对 若i是负数,与左边比他小的形成逆序对 所以两边取较小的 若序列中出现重复的最大值 那么最优解的最大值一定是 先是若干个负数,然…

D. Jeff and Furik time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output Jeff has become friends with Furik. Now these two are going to play one quite amusing game. At the beginning of the game Je…

http://codeforces.com/contest/351/problem/B 题意: 给出一个n的排列 第一个人任选两个相邻数交换位置 第二个人有一半的概率交换相邻的第一个数>第二个数的位置:有一半的概率交换相邻第一个数<第二个数的位置 然后两人轮换 问使序列升序,期望最少操作次数 序列升序即逆序对数为0 dp[i]表示 当前逆序对还剩i对时,先手期望最少操作次数 先手在最优解的情况下一定交换 第一个数>第二个数的位置,即减少1个逆序对 后手等概率增加或减少1个逆序对 dp[i…

B. Jeff and Furik time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output Jeff has become friends with Furik. Now these two are going to play one quite amusing game. At the beginning of the game Je…

The set [1,2,3,-,n] contains a total of n! unique permutations. By listing and labeling all of the permutations in order,We get the following sequence (ie, for n = 3): "123" "132" "213" "231" "312" "3…

Given a string s, return all the palindromic permutations (without duplicates) of it. Return an empty list if no palindromic permutation could be form. For example: Given s = "aabb", return ["abba", "baab"]. Given s = "a…

Given a string, determine if a permutation of the string could form a palindrome. For example,"code" -> False, "aab" -> True, "carerac" -> True. Hint: Consider the palindromes of odd vs even length. What difference d…

The set [1,2,3,…,n] contains a total of n! unique permutations. By listing and labeling all of the permutations in order,We get the following sequence (ie, for n = 3): "123" "132" "213" "231" "312" "3…

Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers. If such arrangement is not possible, it must rearrange it as the lowest possible order (ie, sorted in ascending order). The replaceme…