通过传地址，传引用交换两个数的值

 1 #include <cstdio>
 2 #include <iostream>
 3 using namespace std;
 4 
 5 void swapxy(char *a ,char *b)
 6 {
 7     int c = *a;
 8     *a = *b;
 9     *b = c;
10 }
11 void swapxy(char &a,char &b)
12 {
13     int c = a;
14     a = b;
15     b = c;
16 }
17 
18 
19 int main()
20 {
21     char a = 'f';
22     char b = 'g';
23     
24     swapxy(&a,&b);
25     printf("a = %c, b = %c\n",a,b);
26 
27     char &x = a;
28     char &y = b;
29 
30     swapxy(x,y);
31     printf("a = %c, b = %c\n",a,b);
32 
33     return 0;
34 }