求素数

下面代码仅供本人复习所用，实用性N低，各位飘过吧~~哈哈:>

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//

// 求素数.

//

 

#include <cstdlib>

#include <cmath>

#include <iostream>

#include <vector>

#include <iomanip>

 

typedef std::vector<unsigned long> Primer;

 

//

// 将 range 范围内的素数保存到向量 primer 中.

// 当一个数除以 2 直到到它的平方根时都没有整除，则该数为素数.

//

void getPrimer(Primer &primer, const unsigned long range)

{

    bool isPrimer = false;

    double square_root;

     

    for (unsigned long i = 2, j; i <= range; ++i)

    {

        isPrimer = true;

        square_root = sqrt(i);

        for (j = 2; j <= square_root; ++j)

        {

            if (0 == i % j) {

                isPrimer = false;

                break;

            }

        }

        if (true == isPrimer) {

            primer.push_back(i);

        }

    }

}

 

//

// 测试.

//

int main(void)

{

    unsigned long range;

    Primer primer;

     

    std::cout << "Please input primer solving range: ";

    while (!(std::cin >> range)) {

        std::cout << "Input wrong, input again: ";

    }

     

    getPrimer(primer, range);

     

    Primer::iterator beg = primer.begin();

    Primer::iterator end = primer.end();

    while (beg != end) {

        std::cout << *beg++ << " ";

    }

    std::cout << std::endl;

     

    return EXIT_SUCCESS;

}