实验三

#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() % 31+1;
printf("%3d", x);
}

printf("\n");

return 0;
}

#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>
int main()
{
int x, ans,i;

srand(time(0));
x = rand() % 31+1;
printf("猜猜2021年5月哪一天会是你的luck day\n");

printf("开始咯，你有三次机会，猜吧（1~31）： \n");

for(i=1;i<=3;i++)
{
scanf("%d",&ans);
if (ans>x){
printf("你猜的日期晚了，luck day 悄悄溜到前面啦\n");
printf("再猜(1~31): ");
}
else if (ans<x ){
printf("你猜的日期早啦，luck day 还没到呢\n");
printf("再猜(1~31): ");
}
else {
printf("恭喜你猜对啦\n") ;break;
}
}
if (i>3)
{
printf("次数用完啦。偷偷告诉你：5月你的luck day 是：%3d",x);
}


printf("\n");

return 0;
}

#include<stdio.h>

int main(){
long s ;

while ( printf("Enter your number: "),scanf("%ld",&s)!=EOF){
long ans=0;
int i=1,n;
while(s!=0){
n=s%10;
if(n%2!=0) {

ans=ans+n*i;
i=i*10;
}
s=s/10;

}
printf("New number is: %ld\n",ans);

}

return 0;

}

#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); // 函数调用
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>
#include<math.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 ans;
int i=1,a,sign=1;
for(a=1;i<=n;i++)
{
a=a*i;
ans=ans+sign*1.0/a;
sign=-sign;

}
return ans;

}

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