Problem Description Given a positive integer N, your task is to calculate the sum of the positive integers less than N which are not coprime to N. A is said to be coprime to B if A, B share no common positive divisors except 1.   Input For each test…

题目链接 分析: 要求的是小于$n$的和$n$不互质的数字之和...那么我们先求出和$n$互质的数字之和,然后减一减就好了... $\sum _{i=1}^{n} i[gcd(i,n)==1]=\left \lfloor \frac{n\phi(n)}{2} \right \rfloor$ 考虑$gcd(n,i)=1$,那么必然有$gcd(n,n-i)=1$,然后发现如果把$gcd(n,i)=1$和$gcd(n,n-i)=1$凑到一起会出现$n$,这样的有$\left \lfloor \frac…

FatMouse' Trade Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 56784    Accepted Submission(s): 19009 Problem Description FatMouse prepared M pounds of cat food, ready to trade with the cats g…

Nasty Hacks Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 3049    Accepted Submission(s): 2364 Problem Description You are the CEO of Nasty Hacks Inc., a company that creates small pieces of…

Box of Bricks Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 5994    Accepted Submission(s): 2599 Problem Description Little Bob likes playing with his box of bricks. He puts the bricks one up…

Problem Description Contest time again! How excited it is to see balloons floating around. But to tell you a secret, the judges' favorite time is guessing the most popular problem. When the contest is over, they will count the balloons of each color…

卧槽....最近刷的cf上有最短路,本来想拿这题复习一下.... 题意就是在输出最短路的情况下,经过每个节点会增加税收,另外要字典序输出,注意a到b和b到a的权值不同 然后就是处理字典序的问题,当松弛时发现相同值的时候,判断两条路径的字典序 代码 #include "stdio.h" const int MAXN=110; const int INF=10000000; bool vis[MAXN]; int pre[MAXN]; int cost[MAXN][MAXN],lowcos…

Rectangles    HDOJ(2056) http://acm.hdu.edu.cn/showproblem.php?pid=2056 题目描述:给2条线段,分别构成2个矩形,求2个矩形相交面积. 算法:先用快速排斥判断2个矩形是否相交.若不相交,面积为0.若相交,将x坐标排序去中间2个值之差,y坐标也一样.最后将2个差相乘得到最后结果. 这题是我大一的时候做过的,当时一看觉得很水,写起来发现其实没我想的那么水.分了好几类情况没做出来.今天看了点关于判断线段相交的知识,想起了这题便拿来练…

前言 不说话,先猛戳 Ranklist 看我排名. 这是用 node 自动刷题大概半天的 "战绩",本文就来为大家简单讲解下如何用 node 做一个 "自动AC机". 过程 先来扯扯 oj(online judge).计算机学院的同学应该对 ACM 都不会陌生,ACM 竞赛是拼算法以及数据结构的比赛,而 oj 正是练习 ACM 的 "场地".国内比较有名的 oj 有 poj.zoj 以及 hdoj 等等,这里我选了 hdoj (完全是因为本地上…

题意:有n个点,问其中某一对点的距离最小是多少 分析:分治法解决问题:先按照x坐标排序,求解(left, mid)和(mid+1, right)范围的最小值,然后类似区间合并,分离mid左右的点也求最小值 POJ 3714 #include <cstdio> #include <cstring> #include <cmath> #include <algorithm> const int N = 1e5 + 5; const double INF = 1e…