交换两个变量值（未交换）

#include <stdio.h>
void swap2Variable(int a, int b)
{
  printf("a is %d,b is %d\n", a, b);
  int temp;
  temp = a;
  a = b;
  b = temp;
  printf("a is %d,b is %d\n", a, b);
}

int main()
{
  int num1 = 3, num2 = 5;
  printf("before swap: num1 is %d, num2 is %d\n", num1, num2);
  swap2Variable(num1, num2);
  printf("after swap: num1 is %d, num2 is %d\n", num1, num2); // 函数执行完成后，结果没有变化
}