向上取整:float ceilf(float); double ceil(double);
向下取整:float floorf(float); double floor(double);
四舍五入:float roundf(float); double round(double);
向上取整:float ceilf(float); double ceil(double);
向下取整:float floorf(float); double floor(double);
四舍五入:float roundf(float); double round(double);