不借助第三个变量，交换两个变量值的3种方式

void fun1(){    int a=10,b=100;    a=a+b;    b=a-b    a=a-b;      cout<<"a="<<a<<","<<"b="<<b<<endl；}void fun2(){    int a=10,b=100;    a=a*b;    b=a/b;    a=a/b;      cout<<"a="<<a<<","<<"b="<<b<<endl；}void fun3（）｛    int a=10;int b=100;    a^=b;    b^=a;    a^=b;    cout<<"a="<<a<<","<<"b="<<b<<endl；｝