素数#include<stdio.h>main(){intn,i;/*for(n=100;n<=200;n++){for(i=2;i<=n;i++){if(n%i==0)break;}if(n==i){printf("%d是素数\t",n);}else{printf("%d不是素数\t",n);}}*/printf("请输入n:");scanf("%d",&n);for(i=2;i<=n;i++){if(n%i==0)break;}if(n==i){printf("%d是素数\n",n);}else{printf("%d不是素数\n",n);}}求两个数的最大公约数#include<stdio.h>main(){intm,n,p,r;printf("请输入两个正整数：");scanf("%d%d",&m,&n);if(m<n){p=m;m=n;n=p;}do{r=m%n;m=n;n=r;}while(r!=0);printf("两数个的最大公约数为:%d\n",m);}一元二次方程的根#include<stdio.h>#include<math.h>main(){doublex1,x2,a,b,c,p,q,m,r;printf("求一元二次方程a*x*x+b*x+c=0的根\n请输入abc的值:");scanf("%lf%lf%lf",&a,&b,&c);p=-b/2*a;m=b*b-4*a*c;q=sqrt(m)/2*a;r=sqrt(-m)/2*a;if(m>=0){x1=p+q;x2=p-q;printf("实根x1=%.2f\nx2=%.2f\n",x1,x2);}else{printf("虚根x1=%.2f+%.2fi\n",p,r);printf("虚根x2=%.2f-%.2fi\n",p,r);}}杨辉三角#include<stdio.h>main(){inta[10][10],i,j;for(j=0;j<10;j++)for(i=0;i<=j;i++){if(i==0||i==j)a[j][i]=1;elsea[j][i]=a[j-1][i-1]+a[j-1][i];}for(j=0;j<10;j++)for(i=0;i<=j;i++){printf("%d\t",a[j][i]);if(j==i)printf("\n");}}回文数#include<stdio.h>#include<string.h>intfun(char*s,char*t){inti,d;d=strlen(s);for(i=0;i<d;i++)t[i]=s[i];for(i=0;i<d;i++){if(t[d+i]==s[d-1-i]);elsereturn0;}return1;}main(){inta;chars[100],t[100];printf("\n请输入字符串s：");scanf("%s",s);a=fun(s,t);if(a)printf("%s是回文数\n",s);elseprintf("%s不是回文数\n",s);}排列#include<stdio.h>main(){inti,j,t;intx[10];printf("请输入10个数：");for(i=0;i<10;i++){scanf("%d",&x[i]);}for(i=0;i<9;i++){for(j=i+1;j<10;j++){if(x[i]<x[j]){t=x[i];x[i]=x[j];x[j]=t;}}}printf("这10个数从大到小的排列顺序为：");for(i=0;i<10;i++){printf("%d\t",x[i]);}}