國立暨南國際大學 108 學年度第一學期期末考試卷

1. (10%) Consider the following code.  If the input is

   1 5 3 5
   23 59 0 34
   21 33 21 10
   0 0 0 0

   What will be the output?
   // 11677 - Alarm Clock
   #include <iostream>
   using std::cin;
   using std::cout;
   using std::endl;
   
   struct TIME {
       unsigned short h;
       unsigned short m;
   };
   
   short diff (TIME t1, TIME t2) {
       short result = (t2.h*60+t2.m) - (t1.h*60+t1.m);
       if (result < 0)
           result += 24*60;
       return result;
   }
   
   int main() {
       TIME t1, t2;
       while (true) {
           cin  >> t1.h >> t1.m >> t2.h >> t2.m;
           if (t1.h*t1.h + t1.m*t1.m + t2.h*t2.h + t2.m*t2.m == 0)
               break;
           cout << diff(t1, t2) << endl;
       }
       return 0;
   }
   
   
2. (10%) Determine whether the syntax of the following code is correct or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   // Bitwise Operator & ASCII code
   #include <iostream>
   int main()
   {
      char d = 'T';       std::cout << d;
      d |= 'k';
      d &= 0x57;          std::cout << d;
      std::cout << std::endl;
      return 0;
   }
   
   
3. (10%) Determine whether the syntax of the following code is correct or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   // switch case
   #include <iostream>
   using std::cin;
   using std::cout;
   using std::endl;
   
   int main()
   {
       char s[] = "UNIVERSITY";
       short odd = 0, even = 0;
       for (int i=0; i<sizeof(s); ++i)
           switch (s[i] % 2) {
               case 0:
                   ++even;
                   break;
               case 1:
                   ++odd;
                   break;
           }
       cout << odd << even << endl;
       return 0;
   }
   
   
4. (10%) Determine whether the syntax of the following code is correct or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   // cout starts printing until \0
   #include <iostream>
   using std::cout;
   using std::endl;
   int main()
   {
      char s[] = "Lannister always pays his debts";
      for (char* i=s; *i; ++i)
          if (*i==' ')
              *i = '\0';
      void* p = s;
      cout << static_cast<char*>(p) << endl;
      p = static_cast<double*>(p) + 3;
      cout << static_cast<char*>(p) << endl;
      return 0;
   }
   
   
5. (10%) What will the following code display?
   
   // Static Variables
   #include <iostream>
   using std::cout;
   using std::endl;
   
   void g()
   {
       static int a = 2020;
       static int b =  109;
       int c = a % b;
       a = b; b = c;
       std::cout << a << ' ';
   }
   
   int main()
   {
       for (int i=0; i<6; ++i)
           g();
       return 0;
   }


6. (10%) Consider the following code.  If for input text "WrgdbLvPrqgdb", key values -3, 23, 75 can all translate the text to "TodayIsMonday", what should be the expression (6) that you should supply in the enc() function?
   #include <iostream>
   #include <cstring>
   using std::cout;
   using std::cin;
   using std::endl;
   
   int enc(char c, int k)
   {
       int n;
       if (65 <= c && c <=90)
       {
           n = c - 65;
           n = _____(6)_____
           while (n < 0)
               n += 26;
           c = n + 65;
       }
       if (97<=c && c<=122)
       {
           n = c - 97;
           n = _____(6)_____
           while (n < 0)
               n += 26;
           c = n + 97;
       }
       return c;
   }
   
   int main()
   {
       char msg[40];
       int key;
       cout << "Plaintext? ";
       cin >> msg;
       cout << "key? ";
       cin >> key;
   
       for (int i=0; i<strlen(msg); ++i)
           cout << static_cast<char>( enc(msg[i], key) );
       cout << endl;
       return 0;
   }
   
   
7. (10%) Determine whether the syntax of the following code is correct or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   //  name[i] = *(name + i)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       int a[3][3] = { {8, 1, 6}, {3, 5, 7}, {4, 9, 2} };
       int* b[3] = { a[0], a[1], a[2] };
       cout << *(a[0 + 1]) << *(a[0] + 1) << *(a[0]) + 1 << endl;
       cout << b[1][0]     << b[0][1]     << b[0][0] + 1 << endl;
       return 0;
   }
   
   
8. (10%) What will the following code display?
   
   // Recursive Function
   #include <iostream>
   using std::cout;
   using std::endl;
   
   void d2h(int n, int b)
   {
       char c = n % b;
       if (n >= b)
           d2h(n / b, b);
       c = c<10?c+48:c+55;
       cout << c;
   }
   
   int main()
   {
       d2h(88, 8);    cout << endl;
       d2h(255, 16);  cout << endl;
       d2h(288, 17);  cout << endl;
       return 0;
   }
   
   
9. (10%) Determine whether the syntax of the following code is correct or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   // Pointer to Pointer
   #include <iostream>
   using std::cout;
   using std::cin;
   using std::endl;
   
   int main()
   {
       int a[3][3] = { {8, 1, 6}, {3, 5, 7}, {4, 9, 2} };
       int* p1 = a[0];
       int** p3 = &p1;
       cout << (*p1)+1 << *(p1+1) << *(*p3+2) << endl;
       return 0;
   }
   
   
10. (10%) What will the following code display?
    
    // Tree
    #include <iostream>
    
    struct TREE
    {
       TREE* left;
       char ch;
       TREE* right;
    };
    
    void print(TREE* p)
    {
       if (p != NULL)
       {
           print(p->left);
           std::cout << p->ch;
           print(p->right);
       }
    }
    
    TREE* createTree()
    {
      TREE temp = {NULL, 'G', NULL};
      TREE* g = new TREE( temp );
      TREE* c = new TREE; c->left = NULL; c->ch='C'; c->right = g;
      TREE* a = new TREE; a->left = NULL; a->ch='A'; a->right = c;
      return a;
    }
    
    unsigned max(unsigned a, unsigned b)
    { return (a>b)?a:b; }
    
    unsigned h(TREE* p)
    {
       if (p == NULL)
           return 0;
       else
           return max(h(p->left), h(p->right)) + 1;
    }
    
    int main()
    {
        TREE* p = NULL;
        p = createTree();
        std::cout << h(p);
        p = p->right; std::cout << h(p);
        p = p->right; std::cout << h(p) << std::endl;
        return 0;
    }