1 引入辅助变量法
int a = 1; int b = 2; int c;
c = a; a = b; b = c;
2 代数和法
int a = 1; int b = 2;
a = a+b; b = a-b; a = a-b;
3 逻辑运算法
int a = 1; int b = 2;
a=a^b; b=a^b; a = a^b;
4 运算符优先级法(适用于java, C#, C, C++)
int a = 1; int b = 2;
a = b + 0*(b=a);