國立暨南國際大學 105 學年度第二學期 第二次期中考試卷

1. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   
   // Class definition (P.279)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   class CRational
   {
   public:
       int numerator;      // 分子
       int denominator;    // 分母
   
       void Print()
       {
           cout << numerator << '/' << denominator << endl;
       }
   }
   
   int main()
   {
       CRational a, b, c;
       a.numerator = 1; a.denominator = 2; a.Print();
       b.numerator = 1; b.denominator = 3; b.Print();
       c.numerator = 1; c.denominator = 4; c.Print();
       return 0;
   }
   
   
2. (10%) What will be the output of the following program?
   // Copy Constructor (P.317)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   class CRational
   {
   public:
       int numerator;      // 分子
       int denominator;    // 分母
   
       void Print()
       {
           cout << numerator << '/' << denominator << endl;
       }
   
       CRational() {}      // default constructor
       CRational(const CRational &r)
       {
           numerator   = r.numerator;
           denominator = r.denominator + 1;
       }
   };
   
   int main()
   {
       CRational a; a.numerator = 1; a.denominator = 2;
       CRational b(a);
       CRational c = a;
       CRational d; d = a;
   
       a.Print();
       b.Print();
       c.Print();
       d.Print();
       return 0;
   }
   
   
3. (10%) What will be the output of the following program?
   
   // Default values for constructor arguments (P.228)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   class CRational
   {
   public:
       int numerator;      // 分子
       int denominator;    // 分母
   
       void Print()
       {
           cout << numerator << '/' << denominator << endl;
       }
   
       CRational(int p = 0, int q = 1)
       {
           numerator = p; denominator = q;
       }
   
       CRational(const CRational &r)
       {
           numerator   = r.numerator;
           denominator = r.denominator;
       }
   };
   
   int main()
   {
       CRational a(1, 2);
       CRational b(3);
       CRational c = a;
       CRational d(b);
   
       a.Print();
       b.Print();
       c.Print();
       d.Print();
       return 0;
   }
   
   
4. (10%) What will be the output of the following program?
   
   // Overloading the Decrement Operator (P.348)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   class CRational
   {
   public:
       int numerator;      // 分子
       int denominator;    // 分母
   
       void Print()
       {
           cout << numerator << '/' << denominator << endl;
       }
   
       CRational(int p = 0, int q = 1)
       {
           numerator = p; denominator = q;
       }
   
       CRational& operator--()
       {
           denominator--;
           return *this;
       }
   
       CRational operator--(int)
       {
           CRational r(*this);
           numerator--;
           return r;
       }
   };
   
   int main()
   {
       CRational a(5, 12);
   
       a.Print();
       (--a).Print();
       a--.Print();
       a.Print();
       return 0;
   }
   
   
   
5. (10%) What will be the output of the following program?
   
   // Overloading the Addition Operator (P.344)
   #include <iostream>
   #include <iostream>
   using std::cout;
   using std::endl;
   
   class CRational
   {
   public:
       int numerator;      // 分子
       int denominator;    // 分母
   
       void Print()
       {
           cout << numerator << '/' << denominator << endl;
       }
   
       CRational(int p = 0, int q = 1)
       {
           numerator = p; denominator = q;
       }
   
       CRational operator+(CRational b)  const   // const member function (P.307)
       {
           return CRational( numerator*b.denominator + denominator*b.numerator,
                   denominator * b.denominator );
       }
   
       CRational& operator-(CRational b)   // Return a reference (P.341)
       {
           numerator = numerator*b.denominator - denominator*b.numerator;
           denominator = denominator * b.denominator;
           return *this;
       }
   };
   
   int main()
   {
       CRational a(1, 2);
       CRational b(1, 3);
       CRational c(1, 4);
       CRational d(1, 5);
       CRational e, f;
   
       e = a + b + c + d;
       f = a - b - c - d;
       e.Print();
       f.Print();
       a.Print();
       return 0;
   }
   
   
   
6. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   
   // Static data members (P.311)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   class CNode
   {
   public:
       int value;
       CNode* previous;
       static CNode* pLastNode;
   
       CNode(int v) :
       value(v), previous(pLastNode)
       { pLastNode = this; }
   };
   
   CNode* CNode::pLastNode = NULL;
   
   int main()
   {
       CNode a(3), b(5), c(7);
       CNode* p;
       int n = 0;
   
       for (n=0, p=CNode::pLastNode; p!=NULL; p=p->previous)
           n++;
       cout << n << endl;
      
       return 0;
   }
   
   
   
7. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   
   // Using pointers with a class (P.274)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   class CNode
   {
   public:
       int value;
       CNode* previous;
       static CNode* pLastNode;
   
       CNode(int v) :
       value(v), previous(pLastNode)
       { pLastNode = this; }
   };
   
   CNode* CNode::pLastNode = NULL;
   
   int main()
   {
       CNode a(3), b(5), c(7), d(9), e(11);
       CNode* p;
       int n = 0;
   
       for (n=0, p=&d; p!=NULL; p=p->previous)
           n++;
       cout << n << endl;
      
       return 0;
   }
   
   
   

8. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   
   // Sorting Rational Numbers (P.508)
   #include <iostream>
   #include <vector>
   #include <algorithm>
   using std::vector;
   using std::cout;
   using std::endl;
   
   class CRational
   {
   public:
       int numerator;      // 分子
       int denominator;    // 分母
   
       void Print()
       {
           cout << numerator << '/' << denominator << endl;
       }
   
       CRational(int p = 0, int q = 1)
       {
           numerator = p; denominator = q;
       }
   
       CRational operator+(CRational b)  const   // const member function (P.307)
       {
           return CRational( numerator*b.denominator + denominator*b.numerator,
                   denominator * b.denominator );
       }
   
       CRational& operator-(CRational b)   // Return a reference (P.341)
       {
           numerator = numerator*b.denominator - denominator*b.numerator;
           denominator = denominator * b.denominator;
           return *this;
       }
   };
   
   bool Less(CRational a, CRational b)
   {
       return a.numerator*b.denominator < b.numerator*a.denominator;
   }
   
   int main()
   {
       int b[] = { 1, 3, 5, 7, 2, 4, 6 };
       vector<CRational> a;
       for (size_t i=0; i<(sizeof b / sizeof b[0]); i++)
           a.push_back( CRational(1, b[i]) );
   
       sort(a.begin(), a.end(), Less);
       for (size_t i=0; i<a.size(); i++)
           a.at(i).Print();
   
       return 0;
   }
   
   

9. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).

   // String Methods (P.405)
   #include <iostream>
   #include <iostream>
   #include <string>
   #include <vector>
   using std::vector;
   using std::string;
   using std::cout;
   using std::endl;
   
   class CDiagonal {
   public:
       int x1;
       int y1;
       int x2;
       int y2;
   
       CDiagonal(int a=0, int b=0, int c=0, int d=0):
           x1(a), y1(b), x2(c), y2(d) {}
   };
   
   string getDiagonal(vector<string> tabula, CDiagonal pos)
   {
       string s = string(1, tabula[pos.x1][pos.y1]) +
                   string(1, tabula[pos.x2][pos.y2]);
       return s;
   }
   
   CDiagonal findDiagonal(vector<string> tabula, string s)
   { // s is a 2-character string
       char c1 = s[0];
       char c2 = s[1];
       int x1, y1, x2, y2;
       for (x1=0; x1<5; x1++)
       {
           y1 = tabula[x1].find(c1);
           if (y1 != string::npos) break;
       }
       for (x2=0; x2<5; x2++)
       {
           y2 = tabula[x2].find(c2);
           if (y2 != string::npos) break;
       }
       return CDiagonal(x1, y1, x2, y2);
   }
   
   string enc(string s, vector<string> tabula)
   {
       string ciphertext, c3c4;
       CDiagonal pos, pos2;
       for (size_t i=0; i<s.length()-1; i+=2)
       {
           pos = findDiagonal(tabula, s.substr(i,2));
           pos2.x1 = pos.x1;
           pos2.y1 = pos.y2;
           pos2.x2 = pos.x2;
           pos2.y2 = pos.y1;
           c3c4 = getDiagonal(tabula, pos2);
           ciphertext += c3c4;
       }
       return ciphertext;
   }
   
   int main()
   {
       string plaintext = "PXMMCTUBACSJNO";
       string ciphertext;
       string s("ABCDEFGHIJKLMNOPQRSTUVWXY");
       vector<string> t;
       for (size_t i=0; i<5; i++)
           t.push_back(s.substr(i*5, 5));
       ciphertext = enc(plaintext, t);
       cout << ciphertext << endl;
       return 0;
   }
   

10. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
    // Inheritance (P.433)
    #include <iostream>
    #include <vector>
    #include <string>
    using std::string;
    using std::vector;
    using std::cout;
    using std::endl;
    
    class MyString : public string {
    public:
        MyString(string s): string(s) {}
    
        vector<string> split(char sep = ' ') {
            vector<string> a;
            int anchor = 0;
            size_t pos;
            pos = this->find(sep, anchor);
            while (pos != string::npos) {
                a.push_back( this->substr(anchor, pos-anchor) );
                anchor = pos + 1;
                pos = this->find(sep, anchor);
            }
            a.push_back( this->substr(anchor) );
            return a;
        }
    };
    
    int main()
    {
        MyString s("1 2 3 4 5 6 5 4 3");
        vector<string> arr = s.split();
        for (size_t i=0; i<arr.size(); i++)
            cout << arr.at(i) << endl;
        return 0;
    }
    

11. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
    // Map (P.543)
    #include <iostream>
    #include <map>
    #include <vector>
    #include <string>
    using std::string;
    using std::vector;
    using std::map;
    using std::cout;
    using std::endl;
    
    class MyString : public string {
    public:
        MyString(string s): string(s) {}
    
        vector<MyString> split(char sep = ' ') {
            vector<MyString> a;
            int anchor = 0;
            size_t pos;
            pos = this->find(sep, anchor);
            while (pos != string::npos) {
                a.push_back( this->substr(anchor, pos-anchor) );
                anchor = pos + 1;
                pos = this->find(sep, anchor);
            }
            a.push_back( this->substr(anchor) );
            return a;
        }
    
        int unique() {
            vector<MyString> arr = this->split();
            map<MyString, int> Count;
            for (size_t i=0; i<arr.size(); i++)
            {
                MyString k = arr[i];
                map<MyString,int>::iterator iter = Count.find(k);
                if (iter == Count.end())
                    Count[k] = 1;
                else
                    Count[k]++;
            }
            return Count.size();
        }
    };
    
    int main()
    {
        MyString s("1 2 3 4 5 6 5 4 3 7");
        MyString t("0 4 9 2 9 1 0 9 6 0");
        cout << s.unique() << endl;
        cout << t.unique() << endl;
        return 0;
    }