实验三

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

//生成N个0~9之间的随机整数，并打印输出
#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;
}

 

#include <stdio.h>
int main()
{
int i,j;
int count=0;

for(i=101;i<=200;i++)
{
for(j=2;j<i;j++)
{
if(i%j==0)
break;
}
if(j>=i)
{
count++;
printf("%d",i);
if(count%5==0)
printf("/n");

}


}
return 0;
}

#include<stdio.h>
#include<math.h>
int main()
{
int m,n;
printf("Enter a number:");
while(scanf("%d",&n)!=EOF)
{
int i=0,s=0;
do
{
m=n%10;
if(n%2!=0)
{
s=s+m*pow(10,i);
i++;
}
n=n/10;
}while(n!=0);
printf("new number is:%d",s);
printf("\n");
printf("Enter a number:");
}
return 0;
}

#include <stdio.h>
#include <math.h>
int main(){
int n, i, factorial = 1;
double s = 0, sign = 1.00000;
printf("输入n(1~10):");
while(scanf("%d",&n) != EOF)
{ for(i=1;i<=n;i++)
{
factorial = factorial * i;
sign = pow(-1,i+1);
s = s + sign/factorial;
continue;
}
printf("n = %d s = %f\n", n, s);

s = 0;
factorial = 1;
sign = 1.00000;
printf("输入n(1~10):");
}
return 0;
}

#include<stdio.h>
#include<time.h>
#include<stdlib.h>
int main()
{
int x,n,i=0;
srand(time(0));
x=1+rand()%31;
printf("猜猜2020年12月哪一天会是你的luck day\n开始喽，你有三次机会，猜吧(1～31):");
while(1)
{
scanf("%d",&n);
if(n==x)
{
printf("恭喜你猜对了");
break;
}
else
{
if(n>x)
printf("你猜的日期晚了，luck day悄悄溜到前面啦");
else
printf("你猜的日期早了，luck day还没到呢");
i=i+1;
if(i>2)
{
printf("\n次数用完了。偷偷告诉你:12月，你的luck day是%d号",x);
break;
}
printf("\n");
printf("再猜(1～31):");
}
}
return 0;
}