int n1 = 10,n2 = 20;
tmp = n1;
n1 = n2;
n2 = tmp;
n1 = n1+n2;
n2 = n1-n2;
n1 = n1-n2;
n2 = n1+(n1+n2) ) * 0;
交换两个变量以及不使用第三个变量
原文：http://www.cnblogs.com/daimianju/p/5456241.html
