Question

C++输出流cout<<fixed<<setprecision(2)怎样才能保留小数点后的两位而不四舍五入？ 谢谢！

比如19.195输出19.19而不是19.20

Answer 1

#include<iostream>
#include<iomanip>
using namespace std;
int main()
 {
double f = 19.195;
cout<<setiosflags(ios::fixed)<<setprecision(2)<<f<<endl;
 }

这样就可以了 

追问

这个它还是19.20，不四舍五入的

追答

抱歉看错了。
_STLP_STATIC_CONSTANT(int, left = 0x0001);
_STLP_STATIC_CONSTANT(int, right = 0x0002);
_STLP_STATIC_CONSTANT(int, internal = 0x0004);
_STLP_STATIC_CONSTANT(int, dec = 0x0008);
_STLP_STATIC_CONSTANT(int, hex = 0x0010);
_STLP_STATIC_CONSTANT(int, oct = 0x0020);
_STLP_STATIC_CONSTANT(int, fixed = 0x0040);
_STLP_STATIC_CONSTANT(int, scientific = 0x0080);
_STLP_STATIC_CONSTANT(int, boolalpha = 0x0100);
_STLP_STATIC_CONSTANT(int, showbase = 0x0200);
_STLP_STATIC_CONSTANT(int, showpoint = 0x0400);
_STLP_STATIC_CONSTANT(int, showpos = 0x0800);
_STLP_STATIC_CONSTANT(int, skipws = 0x1000);
_STLP_STATIC_CONSTANT(int, unitbuf = 0x2000);
_STLP_STATIC_CONSTANT(int, uppercase = 0x4000);
_STLP_STATIC_CONSTANT(int, adjustfield = left | right | internal);
_STLP_STATIC_CONSTANT(int, basefield = dec | hex | oct);
_STLP_STATIC_CONSTANT(int, floatfield = scientific | fixed);
一堆标识都没有找到 不四舍五入的。
转换成string吧。再取吧。只有这样了

追问

这个，怎么改？我编的程序在这，r和h分别是1.5和3，结果21.195，保留两位是21.20，但体积Vb题目要求输出21.19，帮我改下好不？谢谢了！
#include
#include
using namespace std;
int main()
{
double r,h,C1,Sa,Sb,Va,Vb;
cin>>r>>h;
Vb=3.14*r*r*h;
cout<<fixed<<setprecision(2)<<"Vb="<<Vb<<endl;
}

追答

#include
#include
#include
using namespace std;
int main()
{
double r,h,C1,Sa,Sb,Va,Vb;
cin>>r>>h;
Vb=3.14*r*r*h;
char buv[32]={0};
cout << Vb << endl;
sprintf(buv,"%-6lf",Vb);
cout << buv << endl;
char* p = buv;
while(*p!='\0')
{
if(*p=='.')
{
p = p+3;
*p = '\0';
}
else
{
p++;
}
}
cout << buv << endl;
Vb = atof(buv);
cout << Vb << endl;
}
这么改