题意: 给定n个不重复的数, 求出这些数的所有子集, 然后设一个数Ni 为 第i个子集中,最大的数 - 最小的数. 然后将i个 Ni求和, 结果mod 1e9 + 7. 分析: 首先将n个数排列,生成一个单调的数列. 举个例子, 如 1 3 5 7 9. 可以看出 1 作为一个子集中最小的数会有 2^4 - 1 = 15种(1 和 3 5 7 9组合, 3 5 7 9任意的非空子集有2^4 - 1种) , 作为最大的数有2^0 - 1 = 0(因为没有数比1小). 同理 9 作为一个子集中最小的…

C. Do you want a date? time limit per test:2 seconds memory limit per test:256 megabytes input:standard input output:standard output Leha decided to move to a quiet town Vičkopolis, because he was tired by living in Bankopolis. Upon arrival he immedi…

Someday, Drazil wanted to go on date with Varda. Drazil and Varda live on Cartesian plane. Drazil's home is located in point (0, 0) and Varda's home is located in point (a, b). In each step, he can move in a unit distance in horizontal or vertical di…

[题目链接]:http://codeforces.com/contest/810/problem/C [题意] 给你一个集合,它包含a[1],a[2]..a[n]这n个整数 让你求出这个集合的所有子集a的f(a)和 这里的f(a)=集合a中最大和最小元素的差; [题解] 朴素的想法是; 将数组a升序排; 枚举最后的集合中最大和最小的元素是a[i]和a[j](i< j); 则f值是a[j]-a[i]的集合有2^(j-i-1)个; 即a[i+1]..a[j-1]这些元素选和不选-. 然后答案+=2(…

An arithmetic progression is such a non-empty sequence of numbers where the difference between any two successive numbers is constant. This constant number is called common difference. For example, the sequence 3, 7, 11, 15 is an arithmetic progressi…

You are given a sequence of numbers a1, a2, ..., an, and a number m. Check if it is possible to choose a non-empty subsequence aij such that the sum of numbers in this subsequence is divisible by m. Input The first line contains two numbers, n and m…

In the capital city of Berland, Bertown, demonstrations are against the recent election of the King of Berland. Berland opposition, led by Mr. Ovalny, believes that the elections were not fair enough and wants to organize a demonstration at one of th…

Two players play a game. The game is played on a rectangular board with n × m squares. At the beginning of the game two different squares of the board have two chips. The first player's goal is to shift the chips to the same square. The second player…

To confuse the opponents, the Galactic Empire represents fractions in an unusual format. The fractions are represented as two sets of integers. The product of numbers from the first set gives the fraction numerator, the product of numbers from the se…

Prime Number CodeForces - 359C Simon has a prime number x and an array of non-negative integers a1, a2, ..., an. Simon loves fractions very much. Today he wrote out number on a piece of paper. After Simon led all fractions to a common denominator and…