c++ 学习（值传递、引用传递、地址传递）

1. 值传递

• 函数调用时，将实参的值传给形参
• 形参发生改变，不影响实参

2. 引用传递

• 函数调用时，相当于使用形参的名称作为实参的别名，指向同一片内存区域
• 形参发生变化时，影响实参

3. 地址传递

• 函数调用时，将实参的地址传给形参
• 形参地址对应的值发生变化时，影响实参

• 值传递
  
• 引用传递

• 地址传递
  

#include 

using namespace std;

// 指针传递
void swap3(int *a, int *b) {
    int temp = *a;
    *a = *b;
    *b = temp;

    cout << "swap3 function, value of a=" << *a << ";address is:" << a << endl;
    cout << "swap3 function, value of b=" << *b << ";address is:" << b << endl;
}

// 引用传递
void swap2(int &a, int &b) {
    int temp = a;
    a = b;
    b = temp;

    cout << "swap2 function, value of a=" << a << ";address is:" << &a << endl;
    cout << "swap2 function, value of b=" << b << ";address is:" << &b << endl;
}

// 值传递
void swap1(int a, int b) {
    int temp = a;
    a = b;
    b = temp;

    cout << "swap1 function, value of a=" << a << ";address is:" << &a << endl;
    cout << "swap1 function, value of b=" << b << ";address is:" << &b << endl;
}


int main(){
    int a1 = 10;
    int b1 = 20;
    int a2 = 10;
    int b2 = 20;
    int a3 = 10;
    int b3 = 20;
    
    swap1(a1, b1);
    cout << "main function, value of a=" << a1 << ";address is:" << &a1 << endl;
    cout << "main function, value of b=" << b1 << ";address is:" << &b1 << endl << endl;
    
    swap2(a2, b2);
    cout << "main function, value of a=" << a2 << ";address is:" << &a2 << endl;
    cout << "main function, value of b=" << b2 << ";address is:" << &b2 << endl << endl;


    swap3(&a3, &b3);
    cout << "main function, value of a=" << a3 << ";address is:" << &a3 << endl;
    cout << "main function, value of b=" << b3 << ";address is:" << &b3 << endl << endl;
}

swap1 function, value of a=20;address is:0x61fee0
swap1 function, value of b=10;address is:0x61fee4
main function, value of a=10;address is:0x61ff0c
main function, value of b=20;address is:0x61ff08

swap2 function, value of a=20;address is:0x61ff04
swap2 function, value of b=10;address is:0x61ff00
main function, value of a=20;address is:0x61ff04
main function, value of b=10;address is:0x61ff00

swap3 function, value of a=20;address is:0x61fefc
swap3 function, value of b=10;address is:0x61fef8
main function, value of a=20;address is:0x61fefc
main function, value of b=10;address is:0x61fef8