int a=3;
int b=4;交换a和b的值
第一张方法，引入临时变量
int temp;
temp = a;
a = b;
b = temp;
第二种，用加减法
a = a+b;
b = a-b;
a = a-b;
第三种，进行位运算
a = a^b;
b = a^b;
a = a^b;

int a=3;
int b=4;交换a和b的值
第一张方法，引入临时变量
int temp;
temp = a;
a = b;
b = temp;
第二种，用加减法
a = a+b;
b = a-b;
a = a-b;
第三种，进行位运算
a = a^b;
b = a^b;
a = a^b;