描述：设计一个求空间两点距离的函数,要求第2个点的默认值为坐标原点.

#include
float distance(float x1,float y1,float z1,float x2=0,float y2=0,float z2=0){
return (float)(sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)+(z1-z2)*(z1-z2)));
}
void main() {
float x1,y1,z1,x2,y2,z2;
scanf("%f %f %f\n%f %f %f",&x1,&y1,&z1,&x2,&y2,&z2);
printf("%f\n%f\n",distance(x1,y1,z1),distance(x1,y1,z1,x2,y2,z2));
}