实验三

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

int main() {
    int x, n;
    
    srand(time(0));
    
    for(n=1; n<=N; n++) {
        x = rand() % 100;
        printf("%3d", x);
    }
    
    printf("\n");
    
    return 0;
} 

int main() {
    int x,y,i; 
    printf("猜猜2021年5月哪一天会是你的luck day\n");
    srand(time(0));
    x = rand() % 31;
    x++;
    printf("开始喽，你有三次机会，猜吧（1~31）:");

    for(i=1;i<=3;i++){
    
        
            
        
        scanf("%d",&y);
        printf("%d\n",y);
        if(y>x){
            printf("\n");
            printf("你猜的日期晚了，luck day悄悄溜到前面啦\n"); 
            printf("再猜(1~31):");
        } 
        else if(y<x){
            printf("\n");
            printf("你猜的日期早了,luck day还没到呢\n");
            printf("再猜(1~31):");    
        }
        else if(y=x){
            printf("\n");
            printf("你猜中了\n");
            return 0;
        }    
    }
    printf("\n");
    printf("次数用完啦.偷偷告诉你:5月，你的luck day是%d号", x);
    printf("\n");
    return 0;
}

#include <stdio.h>

int main(){
    
    long x,m;
    
    printf("Enter a number:");
    while(scanf("%ld",&x)!=EOF){
        long i=1,t=0;
        while(x!=0){
        
            m=x%10;
            if(m%2==1){
                t=t+m*i;
                i=i*10;
              
            }
          x=x/10;
        }
      printf("new number is:%ld\n",t);
      printf("Enter a number:");
   }
   
   return 0;
}

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

void solve(double a,double b,double c);

int main(){
    double a,b,c;
    printf("Enter a,b,c:");
    
    while(scanf("%lf%lf%lf",&a,&b,&c)!=EOF){
        solve(a,b,c);
        printf("Enter a,b,c:");
    }
    
    return 0;
}

void solve(double a,double b,double c){
    double x1,x2;
    double delta,real,imag;
    
    if(a==0)
        printf("not quadratic equation.\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",x1,x2);
        }
        else{
            real=-b/(2*a);
            imag=sqrt(-delta)/(2*a);
            printf("x1=%.2f + %.2fi,x2=%.2f - %.2fi\n",real,imag,real,imag);
        }
    }
}

#include <stdio.h> 

double fun(int n);

int main(){
    int n;
    double s;
    
    printf("Enter n(1~10):");
    while(scanf("%d",&n)!=EOF){
        s=fun(n);
        printf("n=%d,s=%f\n\n",n,s);
        printf("Enter n(1~10):");
    }
    
    return 0;
}

double fun(int n){
    double i,p=1,q=0;
    for(i=1;i<=n;i++){
        p=p*i;
        q=q+1.0/p;
        p=(-1)*p;
    }
    
    return q;
}

#include<stdio.h>
#include<math.h>
int isprime(int a);
int main(){
    int p,b;
    p=101;
    b=0;
    while(p<=200){
        if(isprime(p)==1){
            printf("%4d",p);
            b=b+1;
            if(b%5==0){
            printf("\n");
        }
         
        }
        p=p+1;
         
    }
    printf("\n100~200素数个数为:%d",b);
}
 
int isprime(int a){
    int i;
    double m;
    m=sqrt(a);
    for(i=2;i<=m;i++){
        if(a%i!=0){
        }
        else if(i>m){
            return 1;
        }
        else return 0;
     
        }
        return 1;
    }