/* * 二次筛素数 * POJ268----Prime Distance(数论,素数筛) */ #include<cstdio> #include<vector> using namespace std; const int maxn = 1000005; typedef long long LL; bool is_prime_small[maxn]; bool is_prime[maxn]; vector <int> res; int main() { LL l,u…

埃拉托斯特尼筛法(sieve of Eratosthenes ) 是古希腊数学家埃拉托斯特尼发明的计算素数的方法.对于求解不大于n的所有素数,我们先找出sqrt(n)内的所有素数p1到pk,其中k = sqrt(n),依次剔除Pi的倍数,剩下的所有数都是素数. 具体操作如上述 图片所示. C++实现 #include<iostream> #include<vector> using namespace std; int main() { int n; cin >> n;…

Prime Distance Time Limit: 2 Seconds      Memory Limit: 65536 KB The branch of mathematics called number theory is about properties of numbers. One of the areas that has captured the interest of number theoreticians for thousands of years is the ques…

题意:求[L,R]中差值最小和最大的相邻素数(区间长度不超过1e6). 由于非素数$n$必然能被一个不超过$\sqrt n$的素数筛掉,因此首先筛出$[1,\sqrt R]$中的全部素数,然后用这些素数去筛$[L,R]$. 注意1不是素数,但不会被筛掉,需要特殊处理(巨坑~~) #include<cstdio> #include<algorithm> using namespace std; typedef long long ll; ,inf=0x3f3f3f3f; ll L,R…

题目链接:http://poj.org/problem?id=2689 Time Limit: 1000MS Memory Limit: 65536K Description The branch of mathematics called number theory is about properties of numbers. One of the areas that has captured the interest of number theoreticians for thousan…

题目大意 给定两个数L和U,要求你求出在区间[L, U] 内所有素数中,相邻两个素数差值最小的两个素数C1和C2以及相邻两个素数差值最大的两个素数D1和D2,并且L-U<1,000,000 题解 由于1<=L< U<=2,147,483,647,直接筛肯定超时,但是题目说L-U<1,000,000,我们可以先筛选出sqrt(2147483647)(约等于46340)内的素数即可,然后再用这些素数把区间[L,U]内的合数筛选掉,最后就可以枚举答案了~~~ 代码: #includ…

题目: http://poj.org/problem?id=3126 困得不行了,没想到敲完一遍直接就A了,16ms,debug环节都没进行.人品啊. #include <stdio.h> #include <string.h> #include <queue> using namespace std; ]; ]; int s, t; void prime_init() { memset(prime, , sizeof(prime)); prime[] = ; ; i…

Prime Distance Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 13961   Accepted: 3725 Description The branch of mathematics called number theory is about properties of numbers. One of the areas that has captured the interest of number th…

The branch of mathematics called number theory is about properties of numbers. One of the areas that has captured the interest of number theoreticians for thousands of years is the question of primality. A prime number is a number that is has no prop…

http://poj.org/problem?id=2689 题意:给出一个大区间[L,U],分别求出该区间内连续的相差最小和相差最大的素数对. 由于L<U<=2147483647,直接筛素数是不行的,数组就开不了.可是能够依据素数筛的原理.我们先筛出sqrt(2147483647)以内的素数,然后拿这些素数去筛[L,U]之间的素数,即两次素数筛.可是L,U还是非常大,但U-L<=1000000,所以进行区间平移,将[L,U]平移为[0,U-L],就能用数组放得下. #include &…