++a和a++

输入：

#include <iostream>using namespace std;main(){   int a = 21;   int c ;   // a 的值在赋值之前不会自增   c = a++;      cout << "Line 1 - Value of a++ is :" << c << endl ;   // 表达式计算之后，a 的值增加 1   cout << "Line 2 - Value of a is :" << a << endl ;   // a 的值在赋值之前自增   c = ++a;     cout << "Line 3 - Value of ++a is  :" << c << endl ;   return 0;}

输出：

Line 1 - Value of a++ is :21Line 2 - Value of a is :22Line 3 - Value of ++a is  :23