long long int llround(double x); long long int llround(float x); long long int llround(long double x); long long int llround(T x); //为整型
llround()函数采用单个参数，并返回long long int类型的值。此函数在<cmath>头文件中定义。
llround()函数将单个参数值取整。
llround()函数返回最接近x的整数值，中间情况下从零舍入。返回的值是long long int类型。
#include <iostream>
#include <cmath>
using namespace std;
int main()
{
long long int result;
double x = 11.16;
result = llround(x);
cout << "llround(" << x << ") = " << result << endl;
x = 13.87;
result = llround(x);
cout << "llround(" << x << ") = " << result << endl;
x = 50.5;
result = llround(x);
cout << "llround(" << x << ") = " << result << endl;
x = -11.16;
result = llround(x);
cout << "llround(" << x << ") = " << result << endl;
x = -13.87;
result = llround(x);
cout << "llround(" << x << ") = " << result << endl;
x = -50.5;
result = llround(x);
cout << "llround(" << x << ") = " << result << endl;
return 0;
}运行该程序时，输出为：
llround(11.16) = 11 llround(13.87) = 14 llround(50.5) = 51 llround(-11.16) = -11 llround(-13.87) = -14 llround(-50.5) = -51
#include <iostream>
#include <cmath>
using namespace std;
int main()
{
int x = 15;
long long int result;
result = llround(x);
cout << "llround(" << x << ") = " << result << endl;
return 0;
}运行该程序时，输出为：
llround(15) = 15
对于整数值，应用llround函数将返回与输入相同的值。所以它在实际中并不常用来表示整数值。