#define swap(x,y) {int s=x;x=y;y=s;}
换行的写法
#define swap(x, y)\int temp = x;\x = y;\y = temp;
#define swap(x,y) {x= x+y;y=x-y;x=x-y;}
#define swap(x,y)\
x=x+y;\
y=x-y;\
x=x-y;\