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;
}

#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() % 32; 
        printf("%3d", x);
    }
    
    printf("\n");
    
    return 0；}

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define N 1
 
int main() {
    int x,n,m; 
    n=0;
    
    printf("猜猜2021年5月哪一天会是你的luck day\n开始喽，你有三次机会，猜吧（1~31)：");
    
    srand(time(0)); 
    
    x = rand() % 32; 

    while(n<3)    
    {
     scanf("%d",&m);
    if(m>x)
    {
    if(n<2) 
    printf("你猜的日期晚了，luck day悄悄溜到前面啦\n再猜:");
    else
    printf("你猜的日期晚了，luck day悄悄溜到前面啦");

    
    }
    
     else if(m<x)
    {
    if(n<2)
    printf("你猜的日期早了，luck day还没到呢\n再猜：");
    else
    printf("你猜的日期早了，luck day还没到呢");
    }
    else
   {
            printf ("猜对了");
          return 0;
   }    
    n++;
    
   }


   
	  printf("\n次数用完啦。偷偷告诉你，5月，你的luck day是%d号",x); 
      return 0;
   
    

}

#include<stdio.h>

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

}

任务四#include <math.h>
#include <stdio.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 p=1,q=0,i;
    
    for(i=1;i<=n;i++){
        q=q+p;
        p=(-1)*p*(1/(i+1));

    }

    return q;
}

#include<stdio.h>
#include<math.h>
int isprime(int n);
int main()
{
    int i,y=0,t=0;
    for(i=101;i<=200;i++)
    {
        if(isprime(i))
            {y++;
             printf("%4d",i);
            if(y%5==0)
            printf("\n");
            t=t+1;
             }
    }
    printf("\n\n");
    printf("100~200之间的素数个数为：%d",t);
    printf("\n");
    return 0;
}
int isprime(int n)
{
    int k;
    for(k=2;k<=sqrt(n);k++)
        if(n%k==0)
            return 0;
        return 1;
}