C++ 函数参数的传递方式

c++++ 函数参数传递有三种方式：按值传递副本，按引用传递引用，按指针传递指针。按值传递不影响实际参数，按引用和指针传递则会影响。

C++ 函数参数的传递方式

在 C++ 中，函数参数可以通过引用、指针或值传递。以下是对每种传递方式的介绍和实际示例：

按值传递 (pass-by-value)

传递函数参数的副本。对副本的任何修改都不会影响传递的实际参数。

void swap(int x, int y) {
  int temp = x;
  x = y;
  y = temp;
}

int main() {
  int a = 10, b = 20;
  std::cout << "Before swap: a = " << a << ", b = " << b << std::endl;
  swap(a, b);  // a 和 b 的副本被传给 swap
  std::cout << "After swap: a = " << a << ", b = " << b << std::endl;
  return 0;
}

输出：

Before swap: a = 10, b = 20
After swap: a = 10, b = 20

按引用传递 (pass-by-reference)

传递函数参数的引用。对引用的任何修改都会影响传递的实际参数。

void swap(int &x, int &y) {
  int temp = x;
  x = y;
  y = temp;
}

int main() {
  int a = 10, b = 20;
  std::cout << "Before swap: a = " << a << ", b = " << b << std::endl;
  swap(a, b);  // a 和 b 的引用被传给 swap
  std::cout << "After swap: a = " << a << ", b = " << b << std::endl;
  return 0;
}

输出：

Before swap: a = 10, b = 20
After swap: a = 20, b = 10

按指针传递 (pass-by-pointer)

传递函数参数的指针。对指针所指向内存的任何修改都会影响传递的实际参数。

void swap(int *x, int *y) {
  int temp = *x;
  *x = *y;
  *y = temp;
}

int main() {
  int a = 10, b = 20;
  std::cout << "Before swap: a = " << a << ", b = " << b << std::endl;
  swap(&a, &b);  // a 和 b 的指针被传给 swap
  std::cout << "After swap: a = " << a << ", b = " << b << std::endl;
  return 0;
}

输出：

Before swap: a = 10, b = 20
After swap: a = 20, b = 10

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