头文件：
函数：round()
格式：T round(T x)

#include<iostream>
#include<cmath>
using namespace std;

int main(){
	cout<<"round(1.3) = "<<round(1.3)<<endl
		<<"round(1.5) = "<<round(1.5)<<endl
		<<"round(-1.3) = "<<round(-1.3)<<endl
		<<"round(-1.5) = "<<round(-1.5)<<endl;
	return 0;
}

输出：

1
2
-1
-2