自己写一个swap函数交换任意两个相同元素值 对空指针的使用 字节大小的判断（一）

 1 #include <stdio.h>
 2 struct Point{
 3     int x;
 4     double y;
 5     Point(int x = 0, double y = 0):x(x), y(y){}
 6     void print(){
 7         printf("(%d, %lf)", x, y);
 8     }
 9 };
10 void swap (char *a, char *b, size_t width){
11     char tmp;
12     while(width--){
13         tmp = *a;
14         *a++ = *b;
15         *b++ = tmp;
16     }
17 }
18 //width是交换两个元素的字节大小，用sizeof 求出
19 void myswap(void *x, void *y, size_t width){
20     swap((char *)x, (char *)y, width);
21 }
22 int main(){
23     int inta = 1, intb = 2;
24     printf("before exchange: inta=%d\tintb=%d\n", inta, intb);
25     //交换整形inta和intb的值
26     myswap(&inta, &intb, sizeof(int));
27     printf("after  exchagge: inta=%d\tintb=%d\n", inta, intb);
28 
29     char chara = ‘a‘, charb = ‘A‘;
30     printf("before exchange: chara=%c\tcharb=%c\n", chara, charb);
31     //交换字符chara和字符charb的值
32     myswap(&chara, &charb, sizeof(char));
33     printf("after  exchagge: chara=%c\tcharb=%c\n", chara, charb);
34 
35     Point pointa(1, 1.1), pointb(3, 3.3);
36     printf("before exchange: pointa="); pointa.print(); 
37     printf("\tpointb="); pointb.print(); printf("\n");
38     //交换结构体pointa和pointb的值
39     myswap(&pointa, &pointb, sizeof(Point));
40     printf("before exchange: pointa="); pointa.print(); 
41     printf("\tpointb="); pointb.print(); printf("\n");
42     return 0;
43 }