要写在一行，分行写要用\#define swap(x, y) x = x + y; y = x - y; x = x - y;或#define swap(x, y) x = x + y;\y = x - y;\x = x - y;
#define 指令只能写在一行里，不管用不用花括号都是这样。要写到多行必须要用续行符 \
