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There are n planets in the planetary system of star X. They orbit star X in circular orbits located in the same plane. Their tangent velocities are constant. Directions of orbiting of all planets are t

题目来源： CodeForces 基准时间限制：2 秒 空间限制：131072 KB 分值: 80 难度：5级算法题 给出一个数组A，经过一次处理，生成一个数组S，数组S中的每个值相当于数组A的累加，比如：A = {1 3 5 6} => S = {1 4 9 15}。如果对生成的数组S再进行一次累加操作，{1 4 9 15} => {1 5 14 29}，现在给出数组A，问进行...

Dashing thro’ the snow, In a one-horse open sleigh, O’er the fields we go, Laughing all the way; Bells on bobtail ring, Making spirits bright; What fun it is to ride and sing A sleighing song t...

一个有n个结点的树，设它的结点分别为v1, v2, …, vn，已知第i个结点vi的度数为di，问满足这样的条件的不同的树有多少棵。给定n，d1, d2, …, dn，编程需要输出满足d(vi)=di的树的个数。Input 第一行是一个正整数n，表示树有n个结点。第二行有n个数，第i个数表示di，即树的第i个结点的度数。其中1<=n<=150，输入数据保证满足条件的树不超过10^...

Long long ago, there was a prosperous kingdom which consisted of n cities and every two cites were connected by an undirected road.However, one day a big monster attacked the kingdom and some roads ...

A permutation p of size n is an array such that every integer from 1 to n occurs exactly once in this array.Let’s call a permutation an almost identity permutation iff there exist at least n - k indice

hannnnah_j is a teacher in WL High school who teaches biology.One day, she wants to test m students, thus she arranges n different seats around a round table.In order to prevent cheating, she thinks th

Given a number N, you are asked to count the number of integers between A and B inclusive which are relatively prime to N. Two integers are said to be co-prime or relatively prime if they have no com

Given 5 integers: a, b, c, d, k, you’re to find x in a…b, y in c…d that GCD(x, y) = k. GCD(x, y) means the greatest common divisor of x and y. Since the number of choices may be very large, you’re only

描述：有一个1n的矩阵 固定第一个数为1 其他填正整数 且相邻数的差不能超过1 求方案数%1e9+7的结果输入一个数n 表示1n的矩阵（n<=10^6）输出一个数 表示方案数%1e9+7的结果输入样例3输出样例5用到一个叫默慈金数的东西，具体描述自行百度。给出递推关系式子。Mn=(2n+1)Mn−1+(3n−3)Mn−2n+2M_{n}=\frac{(2n+1)M_{...