#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;
}
#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#define N 5
int main()
{
int n,x;
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 = 0,
count = 0; //计数
for(i = 100; i<=200; i++)
{
int j = 0;
for(j = 2; j<i; j++)
{
if(i%j == 0) //当i有1和自身以外的因数
break;
}
if(j == i) //当i只能被1和自身整除
{
printf("%d ",i);
count++;
}
}
printf("\n101~200之间共有%d个素数",count);
return 0;
}
#include<stdio.h>
/*思路在注释*/
int main()
{
long int s, //输入,数字不要太大,长整型也是有范围的
n=0; //输出
int i=0,t=1;
printf("Enter a number:");
scanf("%ld",&s);
while(s>0)
{
if(s%10%2!=0) //判断这个数每一位上的数字是否奇数
{
n = n+s%10*t; //s%10即取出最后一位数,并且转到新数数位上
t*=10; //t作为取出数在新数中对应的位值
} //注意n与t在一个if中
s /= 10; //从右向左每一位判断完后,s去掉右一位,当s为个位数,运算完后即跳出循环
}
printf("\nnew number is:%ld",n);
return 0;
}
#include<stdio.h>
#include<math.h>
int main()
{
int i = 1,
n;
double a = 1.0,
sum,
s = 0.0;
printf("Enter n(1~9): ");
scanf("%d",&n);
for(i = 1; i<=n; i++)
{
a = a*i; //每项对应阶乘的值
sum = pow(-1,(i-1))*1/a; //每项的值
s += sum;
}
printf("\nn = %d, s = %lf",n,s);
return 0;
}
#include<stdio.h>
#include<stdlib.h>
#include<time.h>
int main()
{
srand(time(0));
int i = 1, n, x = rand()%31;
printf("猜猜2020年12月哪一天会是你的luck day\n");
printf("开始喽,你有三次机会,猜吧(1~31):");
scanf("%d",&n);
while(n>x && i<3)
{
printf("错了,靠后了\n\n再猜:");
scanf("%d",&n);
i++;
}
while(n<x && i<3)
{
printf("错了,靠前了\n\n再猜:");
scanf("%d",&n);
i++;
}
if(n==x)
{
printf("\n猜对了");
}
if(i==3)
{
printf("次数用完,luck day是%d",x);
}
return 0;
}