实验3

实验1
#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;
}

实验2
#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;
}

实验3
#include<stdio.h>
#include<math.h>
int main()
{
    int n=101;
    int i=2,k=0;
    
    for(n=101;n<=200;++n)
    {
        for(i=2;i<=n/2;++i)
        if(n%i==0)break;
        if(i>n/2)
        {
            printf("%d\t",n);
            k+=1;
            
        }
        
    }    
    printf("\n一共有%d个素数",k);
}

 

实验4
#include<stdio.h> 

int main(){
    long s,m,n;
    float i;
    i=0.1; 
    n=0; 
    printf("Enter a number:");
    scanf("%ld",&s);
    
    while(s>0){ 
        m=s%10;
        s=s/10;
        if(m%2!=0){
            i=10*i;
            n=n+m*i;
        }    
    }
    
    printf("new number is%d",n);
    return 0 ;
}

实验5
#include<stdio.h>

int main()
{
int n;
int i=1;
float s=0,h=1;
printf("Enter n(1~10):");
while(scanf("%d",&n)!=EOF){
for(;i<=n;i++)
{
h=h*i;
if(i>=2)h=-1*h;
s=s+1/h;
}
    printf("n=%d,s=%f\n",n,s);
    printf("Enter n(1~10):");
    return 0;
}

实验6
#include<stdio.h> 
#include<stdlib.h> 
#include<time.h> 

int main(){
    int x,i,a;
    
    srand(time(0));
   
    x=rand()%31+1;
    
    printf("猜猜十二月那一天是你的lucyday\n猜吧，开始喽（1~31）\n"); 
    for(i=1;i<=3;i++) {
        scanf("%d",&a);
        if(a==x){
            printf("恭喜你猜对了"); 
            break; 
        }
        if(a>x)
        printf("你猜的日子晚了，luck day悄悄溜到前面了\n");
        
        if(a<x)
        printf("你猜的日子早了，luck day还没到呢\n");
        
         
        
    } 
    if(i>3) 
    printf("次数用完啦，偷偷告诉你：12月你的Lucy day是：%d号",x); 
    
    
    
    return 0;
}