实现轮筛以在给定范围之间生成素数的 C++ 程序
轮筛法用于在给定范围内查找素数。轮因式分解是一种图形方法,用于手动执行埃拉托色尼筛法的初步操作,将质数与复合数分开。
在这种方法中,最内圈中的质数的倍数与其他圈中的倍数位置相似,形成质数及其倍数的辐条。最内圈中的多个这些质数形成外圈中合数的辐条。
算法
Begin Define max number gen_sieve_primes() Declare c Assign c = 2 For p = 2 to max number If prime[p]==0 prime[p]=1 Mul = p multiply c For Mul less than max number prime[Mul] = -1 Increment c Mul = p multiply c Done Done Print_all_prime() Assign c=0 For i = 0 to max number if (prime[i] == 1) Increment c If c less than 4 Switch(c) Case 1 Print 1st prime number Case 2 Print 2nd prime number Case 3 Print 3rd prime number Else Print nth prime number End
示例代码
#include输出结果using namespace std; #define MAX_NUMBER 40 int prime[MAX_NUMBER]; void gen_sieve_prime(void) { for (int p = 2; p < MAX_NUMBER; p++) { if (prime[p] == 0) prime[p] = 1; int c = 2; int mul = p * c; for (; mul < MAX_NUMBER;) { prime[mul] = -1; c++; mul = p * c; } } } void print_all_prime() { int c = 0; for (int i = 0; i < MAX_NUMBER; i++) { if (prime[i] == 1) { c++; if (c < 4) { switch (c) { case 1: cout << c << "st素数是: " << i << endl; break; case 2: cout << c << "nd素数是: " << i << endl; break; case 3: cout << c << "rd素数是: " << i << endl; break; default: break; } }else cout << c << "th素数是: " << i << endl; } } } int main() { gen_sieve_prime(); print_all_prime(); return 0; }
1st素数是: 2 2nd素数是: 3 3rd素数是: 5 4th素数是: 7 5th素数是: 11 6th素数是: 13 7th素数是: 17 8th素数是: 19 9th素数是: 23 10th素数是: 29 11th素数是: 31 12th素数是: 37