#include <stdio.h>
 
int main()
{
      double firstNumber, secondNumber, temporaryVariable;
 
      printf("输入第一个数字: ");
      scanf("%lf", &firstNumber);
 
      printf("输入第二个数字: ");
      scanf("%lf",&secondNumber);
 
      // 将第一个数的值赋值给 temporaryVariable
      temporaryVariable = firstNumber;
 
      // 第二个数的值赋值给 firstNumber
      firstNumber = secondNumber;
 
      // 将 temporaryVariable 赋值给 secondNumber
      secondNumber = temporaryVariable;
 
      printf("\n交换后, firstNumber = %.2lf\n", firstNumber);
      printf("交换后, secondNumber = %.2lf", secondNumber);
 
      return 0;
}

#include <stdio.h>
 
int main() {
   int a, b;
 
   a = 11;
   b = 99;
 
   printf("交换之前 - \n a = %d, b = %d \n\n", a, b);
 
   a = a + b;  // ( 11 + 99 = 110)  此时 a 的变量为两数之和，b 未改变
   b = a - b;  // ( 110 - 99 = 11)  
   a = a - b;  // ( 110 - 11 = 99)
 
   printf("交换后 - \n a = %d, b = %d \n", a, b);
}