题目链接:https://cn.vjudge.net/problem/LightOJ-1259 题意 给一个整数n,问有多少对素数a和b,使得a+b=n 思路 素数筛 埃氏筛O(nloglogn),这个完全够用,当n=3.5e7时将近一秒(1e8次操作) 欧拉筛O(n) 考虑数论专题过完了就写个模版专题 提交过程 AC 代码 #include <cstdio> #include <cstring> using namespace std; const int maxn=1e7+20…

链接: https://vjudge.net/problem/LightOJ-1259 题意: Goldbach's conjecture is one of the oldest unsolved problems in number theory and in all of mathematics. It states: Every even integer, greater than 2, can be expressed as the sum of two primes [1]. Now…

http://lightoj.com/volume_showproblem.php?problem=1259 题目大意:给你一个数n,这个数能分成两个素数a.b,n = a + b且a<=b,问有几组这样的(a,b) 比较简单的哥德巴赫猜想题,不需要多说,但一般的素数判定会TLE,所以这里用的是素数筛选法 这里需要注意的是筛选出来素数数组的大小 #include<stdio.h> #include<math.h> #include<string.h> #inclu…

题目大意:求讲一个整数n分解为两个素数的方案数. 题目思路:素数打表,后遍历 1-n/2,寻找方案数,需要注意的是:C/C++中 bool类型占用一个字节,int类型占用4个字节,在素数打表中采用bool类型可以节约不少内存. #include<iostream> #include<algorithm> #include<cstring> #include<vector> #include<stdio.h> #include<queue&g…

不想说了 #include <cstdio> #include <iostream> #include <ctime> #include <vector> #include <cmath> #include <map> #include <queue> #include <algorithm> #include <cstring> using namespace std; typedef long…

Goldbach`s Conjecture(LightOJ - 1259)[简单数论][筛法] 标签: 入门讲座题解 数论 题目描述 Goldbach's conjecture is one of the oldest unsolved problems in number theory and in all of mathematics. It states: Every even integer, greater than 2, can be expressed as the sum of…

Goldbach`s Conjecture Goldbach's conjecture is one of the oldest unsolved problems in number theory and in all of mathematics. It states: Every even integer, greater than 2, can be expressed as the sum of two primes [1]. Now your task is to check whe…

一.Description In 1742, Christian Goldbach, a German amateur mathematician, sent a letter to Leonhard Euler in which he made the following conjecture: Every even number greater than 4 can be written as the sum of two odd prime numbers. For example: 8…

题目链接:https://vjudge.net/problem/LightOJ-1370 题意:给你N个欧拉函数值,找出每一个大于等于该欧拉函数值的数,并且要求相加和最小. 题解:因为素数i的欧拉函数值等于i-1,所以我们只要找出大于等于i+1的素数即可. 1 #include<iostream> 2 #include<algorithm> 3 #include<vector> 4 #include<cstring> 5 #include<cstdio…

题意:给出n,问满足a+b=n且a,b都为素数的有多少对 将素数打表,再枚举 #include<iostream> #include<cstdio> #include<cstring> #include <cmath> #include<stack> #include<vector> #include<map> #include<algorithm> #define mod=1e9+7; using names…