C语言 定义调用函数 求分段函数

int sign(int x)

{

 int y;

 scanf("%d",&x);

 if(x>0)

 y=1;

 else if(x==0)//判断语句是==不是=号

 y=0;

 else

 y=-1;

 return y;

}

#include <stdioh>

#include <mathh>

int main(void)

{

int repeat, ri;

double x, y;

scanf("%d", &repeat);

for(ri = 1; ri <= repeat; ri++){

scanf("%lf",&x);

y=x>=0sqrt(x):pow(x+1,2)+2x+1/x;

printf("f(%2f) = %2f\n", x, y);

}

}

这就是个简单的if语句练习啊

double y ;

int x;

if ( x<0 )

{

y=abs(x)/20 ;

}

else if ( x<10 )

{

y=3+exp(x) ;

}

else if ( x< 20 )

{

y = log(x) ;

}

else

然后

1

#include<stdioh>

int main()

{

double x;

while(scanf("%lf",&x) == 1) {

if(x == 0) printf("0\n");

else if(x>0) printf("%lf\n",2x+1);

else printf("%lf\n",1/x);

}

return 0;

}

2

#include<stdioh>

int s[13] = {0,31,28,31,30,31,30,31,31,30,31,30,31};

int main()

{

int y,m,d,i,sum;

while(scanf("%d %d %d",&y,&m,&d) == 3) {

sum = 0;

for(i = 1;i<m;i++) sum += s[i];

sum += d;

if((y%400 == 0 ||(y%100 !=0 && y%4==0)) && m>2) sum ++;

printf("%d\n",sum);

}

return 0;

}

3

#include<stdioh>

int f(int n)

{

if(n == 1) return 1;

else return nf(n-1);

}

int main()

{

printf("%d\n",f(9)-f(7)+f(5)+f(3));

return 0;

}

#include<stdioh>

int main()

{

    int x,y;

scanf("%d",&x);

if(x<-10)

y=0;

else if(x<100) y=5x+1;

else

      y = 5x + 1; //这个表达式的值是什么啊

printf("%d\n",y);

return 0;

}

#include <stdioh>

#include <mathh>

double fun(double x)

{

 if (x<=0)return(-x+3);

  else if(x<1)return 1+xx;

    else  return  2x+sqrt(x);

}

int main()

{

    double x;

    scanf("%lf",&x);

    printf("y=%lf \n",fun(x));

    system("pause");

    return 0;

}