Question

c语言中如何实现如果出现条件A，则执行程序1。如果出现条件B，则执行程序2。比如输入一个条件，求三角形的

比如输入一个条件，求三角形的面积。输入另一个条件，求圆的面积。请给出源代码。

Answer 1

#include<stdio.h>
#include<conio.h>
#include<math.h>
#include<string.h>
#include<stdlib.h>

#define PI 3.1415926

const char* menu[] =
{
"菜 单",
"1.三角面积",
"2.圆的面积",
"3.退出计算"
};

double trangleArea(double a, double b, double c);
double circleArea(double radius);
int showMenu(void);
void inputSelectItem(int choose);

void inputSelectItem(int choose)
{
double a, b, c, radius;

if(choose == 1)
{
printf("请输入三角形三边长(中间用空格分隔):");
scanf("%lf%lf%lf", &a, &b, &c);
printf("三角形面积 = %lf\n", trangleArea(a, b, c));
}
else if(choose == 2)
{
printf("请输入圆的半径:");
scanf("%lf", &radius);
printf("圆的面积 = %lf\n", circleArea(radius));
}
else if(choose == 3)
exit(1);
else
printf("你的选择有误!!\n");
printf("按任意键清屏并返回主菜单\n");
getch();
system("cls");
}

int showMenu(void)
{
int i, length, choose;
char* space = " ";

printf("\n\n");
for(i = 0; i < sizeof(menu)/sizeof(char*); i++)
{
length = strlen(space) - (80 - strlen(menu[i]))/2;
printf("%s%s\n\n", space + length, menu[i]);
if(i == 0)
printf("\n\n");
}

fflush(stdin);
printf("请选择:");
scanf("%d", &choose);

return choose;
}

double circleArea(double radius)
{
if(radius > 0.0)
return PI * radius * radius;
else
return 0;
}

double trangleArea(double a, double b, double c)
{
double area = 0, temp;

if(a+b > c && a+c > b && b+c > a)
{
temp = (a + b + c)/2;
area = sqrt(temp * (temp - a) * (temp - b) * (temp - c));
}

return area;
}

void main(void)
{
while(1)
inputSelectItem(showMenu());
}

Answer 2

char a;
scnaf("%d",&a);
switch(a)
{
case 'A':求三角形;break;
case 'B':求圆形;break;

}

Answer 3

if(条件A)求三角形面积else if(条件B)求圆面积

Answer 4

用switch也行 case 1 case 2的~