方法一:說明:從1至100放入陣列,將非素數置為0; n用來控制輸出,每行輸出五個;# include<stdio.h># include<math.h>void main(){int a[101],i,j,n=0;for(i=1;i<=100;i++)a[i]=i;for(i=1;i<=100;i++){ for(j=2;j<=sqrt(i);j++) { if(a[i]%j==0) a[i]=0; } }for(i=1;i<=100;i++){ if(a[i]!=0) {printf("%d ",a[i]); n++;}if(n%5==0)printf("\n");}}方法二:說明:此方法是將2至100間各數的倍數置為0,則所剩的自然就是素數了;# include<stdio.h># include<math.h>void main(){ int a[101],i,j,n=0; for(i=1;i<=100;i++) a[i]=i;for(j=2;j<=100;j++){ for(i=1;i<=100;i++) { if(a[i]%j==0) a[i]=0; }}for(i=1;i<=100;i++){ if(a[i]!=0){printf("%d",a[i]);n++;} if(n%5==0)printf("\n");}方法三:說明:用goto語句實現;# include<stdio.h># include<math.h>void main(){ int i,j,k;for(i=1;i<=100;) { for(j=2;j<=sqrt(i);j++) { if(i%j==0) goto ab; } printf("%d ",i); n++; if(n%5==0) printf("\n"); ab: i++;} }方法四:說明:用break;語句實現;# include<stdio.h>void main(){ int i,j,k;for(i=1;i<=100;i++) { for(j=2;j<=sqrt(i);j++) { if(i%j==0) break; } if(j>sqrt(i)) {printf("%d ",i); n++} if(n%5==0) printf("\n");}}