程序题

1. 输出

   int a = 4;
   
   int &f(int x) {
       a = a + x;
       return a;
   }
   
   int main() {
       int t = 5;
       cout << f(t) << endl; //a = 9
       f(t) = 20; //a = 20
       cout << f(t) << endl; //a = 25
       t = f(t); //a = 30 t = 30
       cout << f(t) << endl; // a = 60
   }

2. 求下面函数的返回值

   int func(int x) {
     int countx = 0;
     while (x) {
       countx++;
       x = x & (x - 1);
     }
     return countx;
   }

   假定x = 9999。 答案：8

   思路：将x转化为2进制，看含有的1的个数。

3. 输出

   int main()
   {
       int i = 1;
       printf("%d,%d\n", ++i, ++i);    
       printf("%d,%d\n", ++i, i++);   
       printf("%d,%d\n", i++, i++);    
       printf("%d,%d\n", i++, ++i);   
       system("pause");
       return 0;
   }

   3 3 5 3 6 5 8 9

4. 栈内存与文字常量区

   char str1[] = "abc";
   char str2[] = "abc";
   
   const char str3[] = "abc";
   const char str4[] = "abc";
   
   const char *str5 = "abc";
   const char *str6 = "abc";
   
   char *str7 = "abc";
   char *str8 = "abc";
   
   cout << (str1 == str2) << endl;//0  分别指向各自的栈内存
   cout << (str3 == str4) << endl;//0  分别指向各自的栈内存
   
   cout << (str5 == str6) << endl;//1指向文字常量区地址相同
   cout << (str7 == str8) << endl;//1指向文字常量区地址相同

   结果是：0 0 1 1

   解答：str1,str2,str3,str4是数组变量，它们有各自的内存空间；而str5,str6,str7,str8是指针，它们指向相同的常量区域。