#include <stdio.h>
int main() {
int a, b;
char operator;
scanf("%d %d %c", &a, &b, &operator);
switch (operator) {
case '+':
printf("%d", a + b);
break;
case '-':
printf("%d", a - b);
break;
case '*':
printf("%d", a * b);
break;
case '/':
printf("%d", a / b);
break;
}
return 0;
}

#include<stdio.h>
#include<math.h>
int main()
{
double a, b, c, del, x1, x2;
scanf("%lf%lf%lf",&a,&b,&c);
del = b * b - 4 * a * c;
if (del >= 0)
{
x1 = (-b + sqrt(del)) / (2 * a);
x2 = (-b - sqrt(del)) / (2 * a);
if (x1 > x2)
printf("%.2f %.2f", x1, x2);
else
printf("%.2f %.2f",x2,x1);
}
else
{
x1 = -b / (2 * a);
x2 = (sqrt(-del)) / (2 * a);
printf("%.2f+%.2fi %.2f-%.2fi",x1,x2,x1,x2);
}
return 0;
}

第一个
#include<stdio.h>
#include<math.h>
int main()
{
double a, b, c, d, s, area;
scanf("%lf%lf%lf",&a,&b,&c);
if ((a + b > c) && (a + c > b) && (b + c > a))
{
d = a + b + c;
s = 0.5*d;
area = sqrt(s*(s-a)*(s-b)*(s-c));
printf("area=%4.2f\t",area);
}
else
{
printf("error input");
}
return 0;
}

第四个
#include <stdio.h>
#include <stdlib.h>
int main()
{
int n;
scanf("%d",&n);
switch(n)
{case 1:printf("Monday\n");break;
case 2:printf("Tuesday\n");break;
case 3:printf("Wednesday\n");break;
case 4:printf("Thursday\n");break;
case 5:printf("Friday\n");break;
case 6:printf("Saturday\n");break;
case 7:printf("Sunday\n");break;
}
return 0;
}

第二个
#include <stdio.h>
#include <stdlib.h>
int main()
{
int a,b;
char c;
scanf("%d %d\n%c",&a,&b,&c);
switch (c)
{
case'+': printf("%d\n",a+b);break;
case'-' :printf("%d\n",a-b);break;
case'/' :printf("%d\n",a/b);break;
case'*' :printf("%d\n",a*b);
}
return 0;
}

#include <stdio.h>
double calculate_final_cost(int x) {
double final_cost = x;
// 根据金额区间计算优惠
if (x <= 600) {
// 每满100元优惠10元
final_cost -= (x / 100) * 10;
} else if (x <= 1200) {
// 超出600元的部分每满100元优惠15元
final_cost -= ((x - 600) / 100) * 15;
// 少于600元的部分打8.88折
final_cost -= 600 * (1 - 0.888);
} else if (x <= 1800) {
// 超出1200元的部分每满100元优惠20元
final_cost -= ((x - 1200) / 100) * 20;
// 少于1200元的部分打8.33折
final_cost -= 1200 * (1 - 0.833);
} else {
// 超出1800元的部分每满100元优惠30元（此优惠封顶210元）
int extra_discount = (x - 1800) / 100 * 30;
if (extra_discount > 210) {
extra_discount = 210;
}
final_cost -= extra_discount;
// 少于1800元的部分打8折
final_cost -= 1800 * (1 - 0.8);
}
// 将final_cost四舍五入到小数点后两位
final_cost = (int)(final_cost * 100 + 0.5) / 100.0;
return final_cost;
}
int main() {
int x;
printf("请输入购买金额（正整数）：");
scanf("%d", &x);
double final_cost = calculate_final_cost(x);
printf("最终消费：%.2f元\n", final_cost);
return 0;
}

#include <stdio.h>
#include <stdbool.h>
bool isPrime(int num) {
if (num <= 1) {
return false;
}
for (int i = 2; i * i <= num; i++) {
if (num % i == 0) {
return false;
}
}
return true;
}
int main() {
int num;
printf("请输入一个整数：");
scanf("%d", &num);
if (isPrime(num)) {
printf("This is a prime.\n");
} else {
printf("This is not a prime.\n");
}
return 0;
}

#include<stdio.h>
int main( )
{
int n,sum=0;
scanf("%d",&n);
for(int i=1;i<=n;i++)
{
sum+=i;
}
printf("%d",sum);
return 0;
}

#include <stdio.h>
#include <stdlib.h>
int main()
{
int i, n, sum;
sum = 0;
scanf("%d", &n);
for (i = 1; i <= n; i++){
sum += i;
}
printf("%d\n", sum);
return 0;
}

#include "stdio.h"
int main()
{
int i;
double bonus,bon1,bon2,bon4,bon6,bon10;
bon1=100000*0.1;
bon2=bon1+100000*0.075;
bon4=bon2+200000*0.05;
bon6=bon4+200000*0.03;
bon10=bon6+400000*0.015;
scanf("%d",&i);
if (i <=100000)
bonus=i*0.1;
else if (i <=200000)
bonus=bon1+(i-100000)*0.075;
else if (i <=400000)
bonus=bon2+(i-200000)*0.05;
else if (i <=600000)
bonus=bon4+(i-400000)*0.03;
else if (i <=1000000)
bonus=bon6+(i-600000)*0.015;
else
bonus=bon10+(i-1000000)*0.01;
printf("%.f",bonus);
return 0;
}

#inc lude (stdio.h> int main0 [ int c,s;
float p,w, d, char ges;
printf("please enter price, weight, discount:") scanf ("%f,%f,%d",&p,&w, &s): //输入单价、重量、距离if(s>=3500)d=25;//3500km以上为同一折扣el se c=s/250;//3500km以下各段折扣不同，c的值不相同switch(c)
(case 0:d=0;break; //c=0,代表250km以下，折扣d=0
case 1:d=5;break; //c=1,代表250~500km以下，折扣d=5% case 2: case 3: case 4:
case 5:d=10;break;//c=25,代表500~1500km,折扣d=10% case 6: case 7: case 8:
case 9:d=15;break;//c=6~9,代表1500~2500km,折扣d=15% case 10: case 11: case 12:
case 13:d=20;break;//c=8~11,代表2500~3500km,折扣d=20%
char ges=p*w*s*(1-d/100): //计算总运费printf("freight=%10.2fln", charges)://输出总运费，取两位小数return 0;
]
屏幕退出，

第三个
#include <stdio.h>
#include <stdlib.h>
int main()
{int a,i=0;
scanf("%d",&a);
if(a==1)
printf("This is not a prime.");
for (i=a-1;i>1;i--)
{
if(a%i==0)
{
printf("This is not a prime.");
break;
}
}
if(i==1)
printf("This is a prime.");
return 0;
}

#include<stdio.h>
int main() {
int distance;
int discount;
puts("请输入路程");
scanf_s("d%", &distance);
if (distance < 250) {
discount = 0;
}
else if (250 <= distance && 500 > distance) {
discount = 2;
}
else if (500 <= distance && 1000 > distance) {
discount = 5;
}
else if (1000 <= distance && 2000 > distance) {
discount = 8;
}
else if (2000 <= distance && 3000 > distance) {
discount = 10;
}
else if (distance >= 3000) {
discount = 15;
}
/* 注释这段用下面那段，当然这段也可以用，哈哈哈
discount = discount / 100;//折扣为百分比所以除以一百
printf("折扣是：%d",discount);
*/
printf("折扣是：%d", discount/100);//也可以写成这样方便很多
return 0;
}

#include <stdio.h>
double calculate_final_cost(int x) {
double final_cost = x;
// 根据金额区间计算优惠
if (x <= 600) {
// 每满100元优惠10元
final_cost -= (x / 100) * 10;
} else if (x <= 1200) {
// 超出600元的部分每满100元优惠15元
final_cost -= ((x - 600) / 100) * 15;
// 少于600元的部分打8.88折
final_cost -= 600 * (1 - 0.888);
} else if (x <= 1800) {
// 超出1200元的部分每满100元优惠20元
final_cost -= ((x - 1200) / 100) * 20;
// 少于1200元的部分打8.33折
final_cost -= 1200 * (1 - 0.833);
} else {
// 超出1800元的部分每满100元优惠30元（此优惠封顶210元）
int extra_discount = (x - 1800) / 100 * 30;
if (extra_discount > 210) {
extra_discount = 210;
}
final_cost -= extra_discount;
// 少于1800元的部分打8折
final_cost -= 1800 * (1 - 0.8);
}
// 将final_cost四舍五入到小数点后两位
final_cost = (int)(final_cost * 100 + 0.5) / 100.0;
return final_cost;
}
int main() {
int x;
printf("");
scanf("%d", &x);
double final_cost = calculate_final_cost(x);
printf("%.2f\n", final_cost);
return 0;
}