POJ 2739 素数筛选

POJ 2739

   关键是找10000内质数的方法

#include <iostream>using namespace std;void create_primes(int * prime,int &size){//找出10000以内所有的质数，用因子排除法int notPrime[10001] = {false};int i ;for (i = 2; i < 10001 ;i++){int x = i*2;while(x<10001){notPrime[x] = true;x += i;}}for (i = 2; i < 10001;i++){if (!notPrime[i]){prime[size++]=i;}}}int main(){int prime[10000];int sizeofprime = 0;create_primes(prime,sizeofprime);int num,result=0;while (cin >> num,num != 0){for(int i = 0;i < sizeofprime;i++){if (prime[i] > num){break;}int n = num;int index = i;        while(n > 0){n -= prime[index];//反复试探用num减去从某个比之小的质数开始的连续质数看是否可以减为0index++;}if (n == 0)result++;}}cout<<result<<endl;result = 0;}return 0;}