四舍五入
https://www.cnblogs.com/kiritozhj/p/10019292.html
#include <iostream>
#include <stdio.h>
using namespace std;
double round3(double number,int bits) //number->浮点数,bits->保留位数
{
for(int i=0;i<bits;++i)
{
number*=10;
}
number=(long long)(number+0.5);
for(int i=0;i<bits;++i)
{
number/=10;
}
return number;
}
int main()
{
double x;
while(scanf("%lf",&x)!=EOF){
printf("%.2lf\n",round3(x,2));
}
}