实验333333333333333333

#include<math.h>
#include<stdio.h>

int main(){
    float a, b, c, x1, x2;
    float delta, real, imag;
    
    printf("Enter a, b, c: ");
    
    while(scanf("%f%f%f", &a, &b, &c) !=EOF) {
       if(a == 0)
           printf("not quadratic equation.\n\n");
       else {
           delta =b*b -4*a*c;
           
           if(delta >=0 ) {
                  x1 =(-b + sqrt(delta)) /(2*a);
               x2 =(-b + sqrt(delta)) /(2*a);
               printf("x1 = %.2f , x2 = %.2f\n\n" , x1, x2);
           }
           else{
                  real = -b/(2*a); 
               imag = sqrt(-delta) / (2*a);
               printf("x1 = %.2f + %.2fi, x2 = %.2f - %.2fi\n\n" , real, imag, real, imag);
                 }
          }
          
          printf("Enter a, b, c: ");
      }
      
      return 0;
  }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#define N 5

int main() {
    int x, n;
    
    srand(time(0));
    n=0;
    do {
        n++;
        x=rand()%10; 
        printf("%3d",x);    
    }while(n<N);
    
    printf("\n");
    
    return 0;
}

#include <stdio.h>
int main() {
    int n,m,count;
    count==0;
    for(n=100;n<200;n++) 
    { 
    for(m=2;m<=n;m++)
    {
        if(n%m==0)
        {
            break;
        }
    }
    if(n==m)
    {
        count++;
        printf("%d ",n);

     if(count%5==0)
       printf("\n");

      }

  }
    printf("\n这一区间内素数个数:%d\n",count);
     return 0 ;
}

#include<stdio.h>
#include<math.h>
int main()
{
    int m,n;
    printf("Enter a number:");
    while(scanf("%d",&n)!=EOF)
    {
        int i=0,s=0;
        do
        {
            m=n%10;
            if(n%2!=0)
            {
                s=s+m*pow(10,i);
                i++;
            }
        n=n/10;
        }while(n!=0);
    printf("new number is:%d",s);
    printf("\n"); 
    printf("Enter a number:");
    }
    return 0;
}

#include<stdio.h>
#include<math.h>
#include<stdlib.h>
int main(){
    float s,sum;
    int n;

    printf("Enter n(1~10):");
        
    while(scanf("%d",&n)!=EOF){
        
        sum=0.0,s=1.0;
        int i;
        
    for(i=1;i<=n;++i){
        s=s*i;
        sum=sum+pow(-1,i-1.0)/s;
    }
    printf("n=%d,sum=%lf\n",n,sum);
    printf("Enter n(1~10):\n");}
    return 0;
}

#include<stdio.h>
#include<time.h>
#include<stdlib.h>
int main()
{
    int x,n,i=0;
    srand(time(0));
    x=1+rand()%31;
    printf("猜猜2020年12月哪一天会是你的luck day\n开始喽，你有三次机会，猜吧(1～31):");
    while(1)
    {
        scanf("%d",&n);
        if(n==x) 
        {
            printf("恭喜你猜对了");
            break;
        }
        else
        {
            if(n>x) 
                printf("你猜的日期晚了，luck day悄悄溜到前面啦");
            else 
                printf("你猜的日期早了，luck day还没到呢");
            i=i+1;
            if(i>2)
            {
                printf("\n次数用完了。偷偷告诉你:12月，你的luck day是%d号",x);
                break;
            }
            printf("\n");
            printf("再猜(1～31):");
        }
    }
    return 0;
}