增量递减

递增和递减运算符以前缀和后缀形式存在。

int a = 1;
int b = 1;
int tmp = 0;

tmp = ++a;        /* increments a by one, and returns new value; a == 2, tmp == 2  */
tmp = a++;        /* increments a by one, but returns old value; a == 3, tmp == 2 */
tmp = --b;        /* decrements b by one, and returns new value; b == 0, tmp == 0 */
tmp = b--;        /* decrements b by one, but returns old value; b == -1, tmp == 0 */

请注意，算术运算不会引入序列点 ，因此使用++或 -- 运算符的某些表达式可能会引入未定义的行为 。