[Project Euler]加入歐拉 Problem 7

By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6^(th) prime is 13.

What is the 10001^(st) prime number?

 

求第10001個質數。 這個比較簡單，使用一個迴圈就出來了，不到2秒。

歐拉項目第七題#include <stdio.h>#include <stdlib.h>#include <math.h>#include <stdbool.h>bool isPrime(double num);int main(int argc, char *argv[]){    int n = 0;    double num = 2.0;        while(1)    {        if(isPrime(num))        {            n++;            if(n == 10001)            break;        }        num++;    }       printf("%lf", num);  system("PAUSE");  return 0;}bool isPrime(double num){    double sqr = sqrt(num + 1);        unsigned long i = 2;    for(i = 2; i <= sqr; i++)    {        if(fmod(num, i) == 0)        return false;    }        return true;}