素数筛选法(prime seive)

素数筛选法比较有名的,较常用的是Sieve of Eratosthenes,为古希腊数学家埃拉托色尼(Eratosthenes 274B.C.～194B.C.)提出的一种筛选法。详细步骤及图示讲解,还有java与c++版源代码.

 void runEratosthenesSieve(int upperBound) {
     int upperBoundSquareRoot = (int)sqrt((double)upperBound);
     bool *isComposite = new bool[upperBound + ];
     memset(isComposite, , sizeof(bool) * (upperBound + ));
     for (int m = ; m <= upperBoundSquareRoot; m++) {
         if (!isComposite[m]) {
             for (int k = m * m; k <= upperBound; k += m)
                 isComposite[k] = true;
         }
     }
     for (int m = ; m <= upperBound; m++)
         if (!isComposite[m])
             cout << m << " ";
     delete [] isComposite;
 }

素数在信息安全中有着重要应用.