实验三

//shiyanyi
#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;
}

 

 

//shiyaner
#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;
}

 

 

//shiyansan
#include<math.h>

int main()
{
    int i,sum,n,m;
    
    i=0;

    for(n=101;n<=200;n++)
    {
        for(i=2;i<=sqrt(n);++i)
         if(n%i==0)break;
        if(i>sqrt(n))
        {
            printf("%d\t",n);
            sum=sum+1;
            if(sum%5==0)
            printf("\n");
            
        
    }
    printf("101~200");
    
    
     printf("101^200之间共有%d个素数",sum);
    
    

  return 0;

 

 

 

 

//shiyansi
#include<stdio.h>
int main()
{
    int x, y, v, d;
  d = 1;
   v = 0;
    printf("Enter a number:");
       while (scanf("%d", &y) != EOF) {
           while (y>= 1)
          {
              x = y % 10;
            y = y / 10;
              if (x % 2 != 0)
              {
                   v = v+x * d;
                  d = d * 10;
             }
       }
                printf("Enter a new number :%d\n", v);
                v = 0;
            d = 1;
                printf("Enter a number：");
            
        }
    return 0;

 

 

 

//shiyanwu
#include<stido.h>
int main() {
    int  n,d,c;
    float a,b;
    a = 0;
    b = 1;
    c = 1;
    d = 1;
    printf("Enter n(0`10):");
    while(scanf("%d", &n) != EOF) {

        for (; d <= n; d++)
        {
            c = (-1) * c * a;
            a = a - b / c;
        }
        printf("n=%d, s=%f\n\n", c, a);
        printf("Enter n(0`10):");
    }
    return 0;}
    

 

 

//shiyanliu
#include<stdlib.h>
#include<time.h>
int main()
{
    int x, y, c, z;
    srand(time(0));
    x = (rand() % 31 + 1);
    printf("猜猜2020年12月哪一天是你的luck day\n\n");
    printf("开始咯,你有三次机会，猜吧（1~31):");
    scanf("%d", &x);
    printf("\n\n");
    if (y == x)
    {
        printf("luck day");}
    else if (y < x)
    {
        printf("你猜的日期早了，luck day还没到呢");
    }
    else if (y > x)
    {
        printf("你猜的日期晚了，luck day悄悄溜到前面啦");
                              }
    printf("再猜(1~31:)");
    scanf("%d", &c);
    printf("\n");
    if (c == x)
    {
        printf("luck day");
           } 
    else if (c < x){
        printf("你猜的日期早了，luck day还没到呢");
    }
    else if (c > x)
    {
        printf("你猜的日期晚了，luck day悄悄溜到前面啦");
    }
    printf("再猜(1~31:)");
    scanf("%d", z);
    printf("\n\n");
    if (z == x)
    {
        printf("luck day");
    }
    else if (z < x)