int a = 1;
int b = 2;
方法一:
int c = a;
a = b;
b = c;
方法二:
a = a^b;
b = a^b;
a = a^b;
方法三:
a = a+b;
b = a-b;
a = a-b;

int a = 1;
int b = 2;
方法一:
int c = a;
a = b;
b = c;
方法二:
a = a^b;
b = a^b;
a = a^b;
方法三:
a = a+b;
b = a-b;
a = a-b;