不允许创建临时变量，交换两个数的内容

#include<stdio.h>int main(){    //加法实现    int a = 5, b = 7;    a=a+b; //a=12 b=7    b=a-b; //a=12  b=5    a=a-b; //a=7  b=5    printf("a=%d  b=%d\n", a,b);    return 0;}

#include<stdio.h>int main(){    //乘法实现    int a = 5, b = 7;    a=a*b; //a=35 b=7    b=a/b; //a=12  b=5    a=a/b; //a=7  b=5    printf("a=%d  b=%d\n", a,b);    return 0;}

#include<stdio.h>int main(){    //异或实现    int a = 5, b = 7; // 5转换成二进制0101 , 7转换成二进制0111    a=a ^ b; //a=0010 b=0111   "^"异或，相同为1，不同为0    b=a ^ b; //a=0010  b=0101    a=a ^ b; //a=0111  b=0101    printf("a=%d  b=%d\n", a,b);    return 0;}