60STL_bitset埃拉托斯特尼筛法demo

示例代码

示例代码

//埃拉托斯特尼筛法：查找质数 #include <iostream> #include <bitset> #include <cmath> using namespace std; int main() { //用初始化符号()比赋值等号速度快！ int const max_number(10000000); int const max_test((int)sqrt(double(max_number))); //求算数平方根 bitset<max_number+1> numbers; //0不要了，有101个0(0-100) numbers.set(); //101个1 numbers[1] = 0; for(int i(1); i != max_test; ++i) { if(numbers[i]) { for(int j = i*i; j<max_number+1; j+=i) { numbers[j] = 0; } } } cout << "The number of primes less than " << max_number + 1 << " is " << numbers.count() << ".\n\n"; // for(int i = 1; i != max_number+1; ++i) // { // if(numbers[i]) // cout << i << ", "; // } // cout << endl; return 0; }