例3:输入一个大于或等于3的正整数,判断其是否为素数(算法:P28,图223) inO maInt (0 fint n, w, i; Rint n, w, i; w=0;i=2: scanf(“%d”,&n); scanf“%d”,cn); dot for(i=2;i<=n-l.&w==0;i++) if(n%i==0)w=1; if(n%i==0)w=1 else it+ if(w==0) printi(“% d is a prime”, else printf((“% od is not a prime”,n) +while( i<=n-1&& w==0) if(w==0)printf(%d is a prime, n) else printf(“ yod is not a prime”,n) maInt fint n, w,i w=0 whle(i<=n/2&&w==0) scanf“%d”,&n); for(i=2; K<=n-1; i++) while(i<=sqrt(n)&&w==0 if(n%i==0)break; ifi>=n) printf((“% d is a prime”, while(i<=sart(n+l)&&w==0) else printf((“% d is not a prime”,n)例3: 输入一个大于或等于3的正整数, 判断其是否为素数（算法：P28,图2.23) main() {int n,w,i; w=0; i=2; scanf(“%d”,&n); do{ if(n%i = =0) w=1; else i++; } while( i<=n-1&& w= =0) if(w= =0) printf(“%d is a prime”, n) else printf(“%d is not a prime”, n) } while(i<=n/2&& w= =0) while(i<=sqrt(n+1) && w= =0) main() {int n,w,i; w=0; scanf(“%d”,&n); for(i=2; i<=n-1&&w = = 0; i++) if(n%i = =0) w=1; if(w= =0) printf(“%d is a prime”, n) else printf(“%d is not a prime”, n) } while(i<=sqrt(n) && w= =0) main() {int n,w,i; w=0; scanf(“%d”,&n); for(i=2; i<=n-1; i++) if(n%i = =0) break; if(i>=n) printf(“%d is a prime”, n) else printf(“%d is not a prime”, n) }