ＮＹＯＪ１８７快速判断素数

#include<stdio.h>#include<math.h>#define MAX_SIZE 2000001／／注意：define 没有 分号int flag[MAX_SIZE];int main(){int a;int i, j;flag[0] = flag[1] = 1;for(i = 2; i <= sqrt(MAX_SIZE); i ++)//遍历了所有的数并进行标记{if(flag[i] == 0 ){for( j = i + i; j <= MAX_SIZE;j = j + i ){flag[j] = 1;}}}while(scanf("%d",&a) && a != 0 ){printf("2");for(i = 3; i <= a; i ++)if(flag[i] == 0)printf(" %d",i);printf("\n");}return 0;}