实验3

#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 3

int main(){
    int x,y,i,;
    
    srand(time(0));
    x = rand()%31;
    x++;
    
    printf("猜猜2021年5月那一天会是你的luck day\n");
    printf("开始喽，你有三次机会，猜吧（1～31）：");
    
    for(i=1;i<=N;i++){
        if(i>=2){
            printf("再猜：\n");
        }
         scanf("%d",&y);
         if(y>x)
            printf("你猜的日期晚了，luck day悄悄溜到前面啦 \n");
        else if(y<x)
            printf("你猜的日期早了，luck day还没到呢 \n");
        else{
           printf("你猜中了\n") ;
           break;}
        
 }
   printf("次数用完啦，偷偷告诉你：5月，你的luck day是%2d号\n",x) ;
    
    

return 0;
}

#include<stdio.h> 
int main(){
    
    int s,i,x,S=0,n=1;
    printf("enter a number:");
    scanf("%d",&s);
    
    for(i=1;i>0;i++){
    
    x=s%10;
    if(x%2==0)
    s=(s-x)/10;
    else{
    S=S+n*x;
    n=n*10;
    s=(s-x)/10;}
    
    if(s==0)
    break;}
    
    
    printf("new number is:%d\n",S);
    
    
    return 0;
    
}

#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 m=1,p=0,i;
     
    for(i=1;i<=n;i++){
        p=p+m;
        m=(-1)*m*(1/(i+1));
 
    }
 
    return p;
}

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