C++ round()用法及代碼示例

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

int main() {

  // display integral value closest to 15.5
  cout << round(15.5);

  return 0;
}

// Output: 16

round() 語法

用法:

round(double num);

參數：

round() 函數采用以下參數：

• num- 要四舍五入的浮點數。它可以是以下類型：
  • double
  • float
  • long double

返回：

round() 函數返回：

• 最接近 num 的整數值，中間情況從零四舍五入。

round() 原型

cmath 頭文件中定義的 round() 函數的原型是：

double round(double num);

float round(float num);

long double round(long double num);

// for integral type
double round(T num);

示例 1：C++ round()

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

int main() {

  double num, result;

  num = 11.16;
  result = round(num);

  cout << "round(" << num << ") = " << result << endl;

  num = 13.87;
  result = round(num);

  cout << "round(" << num << ") = " << result << endl;
    
  num = 50.5;
  result = round(num);

  cout << "round(" << num << ") = " << result;
      
  return 0;
}

輸出

round(11.16) = 11
round(13.87) = 14
round(50.5) = 51

示例 2：用於負數的 C++ round()

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

int main() {

  double num, result;

  num = -11.16;
  result = round(num);

  cout << "round(" << num << ") = " << result << endl;

  num = -13.87;
  result = round(num);

  cout << "round(" << num << ") = " << result << endl;
    
  num = -50.5;
  result = round(num);

  cout << "round(" << num << ") = " << result;
      
  return 0;
}

輸出

round(-11.16) = -11
round(-13.87) = -14
round(-50.5) = -51

示例 3：用於整數類型的 C++ round()

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

int main() {
  double result;

  int num = 15;
  result = round(num);

  cout << "round(" << num << ") = " << result;

  return 0;
}

輸出

round(15) = 15

對於整數值，應用round() 函數返回與輸入相同的值。所以在實踐中它並不常用於整數值。