找出以下程序中的语法错误，并作出解释。

1.    1 #include <stdlib.h>
      2 int main() {
      3     const int size;
      4     size = 10;
      5     int a[size];
      6     int *p1 = new int[size];
      7     int *p2 = malloc(sizeof(int)* size);
      8     int *p3 = new int(size);
      9     for(int i = 0; i < size; i++) {
     10         a[i] = i;
     11         p1[i] = a[i] * i;
     12         p2[i] = p1[i] * i;
     13         p3[i] = p2[i] * i;
     14     }
     15     int sum;
     16     for(int i = 0; i < size; i++)
     17         sum += a[i] + p1[i] + p2[i] + p3[i];
     18     cout << sum;
     19     delete p1;
     20     delete [] p2;
     21     delete p3;
     22 }
   

2.    1 #include <iostream>
      2 using namespace std;
      3 class N {
      4     static int n = 0;
      5     int i;
      6 public:
      7     void N() : i(0) { }
      8     void N(int a = 0) : i (a) { }
      9     void N(int a = 0, int b) : i(a), n(b) { }
     10     int get() const { return i++; }
     11     void set(int a) { i = a;}
     12     void print() const { cout << get() << endl;}
     13     static int getn() const { return n; }
     14     static void setn(int a) { n = a; i++; }  
     15 }
     16 int main() {
     17     cout << N::n << endl;
     18     cout << N::getn() << endl;
     19     cout << get() << endl;
     20     cout << N::get() << endl;
     21     cout << N::setn(10) << endl;
     22     N *p = new N(5);
     23     N n();
     24     n.set(10);
     25     n.setn(11);
     26     p.set(5);
     27     delete p;
     28 }
   

3.    1 #include <string>
      2 #include <iostream>
      3 using namespace std;
      4 class S {
      5 public:
      6     S(int a0) { cout << a0 << endl; }
      7     S(double a0, int b0) : d(a0), b(b0){ cout << a0 << b0 << endl; }
      8     S(char *p0) : d(a), b(2) { cout << p << endl;} 
      9     S(int &a0) : a(0), b(1), c("abc"), d(r), p(new int) { }
     10 private:
     11     int a;
     12     const int b;
     13     string c;
     14     int &d;
     15     int *p;
     16 };
     17 int main() {
     18     S a(1);
     19     S b;
     20     S c(0.0, 1);
     21     S d("hello");
     22     S e(true);
     23     S f(a);
     24     e = a;
     25 }
   

4.    1 #include <string>
      2 #include <iostream>
      3 using namespace std;
      4 class Person{
      5 public:
      6     Person(string name) : name_ (name) { }
      7     virtual void print() const = 0 { cout << name_; }
      8     virtual bool compare(Person p) const { return p.name_ == name_; }
      9 protected:
     10     string name_;
     11 };
     12 class Student : public Person {
     13     Student(string name, string id) { name_ = name; id_ = id; }
     14     Student(Person p, string id) { name_ = p.name_; id_ = id;}
     15     bool compare(Student s) const { return s.name_==name_ && s.id_ == id_; }
     16     void print() { cout << name_ << id_ << endl; }
     17 private:
     18     string id_;
     19 };
     20 
     21 int main() {
     22     Person p("Mike");
     23     Student s("jack", "12345");
     24     Student t(p, "23424");
     25     cout << s.compare(t);
     26     cout << p.compare(t);
     27     cout << s.compare(p);
     28     s.print();
     29     s.Person::print();
     30 }
   

5.    1 class Integer{
      2 public:
      3     Integer(int a = 0) : i(a) {}
      4     Integer operator+(int a, int b) { return a + b;}
      5     Integer operator-() { return -i; }
      6     Integer operator+() { return i; }
      7     Integer operator++() { return ++i; }
      8     Integer operator++(int) { return i++; }
      9     bool operator<>(int a) { return i != a; }
     10 private:
     11     int i;
     12 };
     13 void operator>>(ostream &os, Integer i) {
     14     os << i;
     15 }
     16 istream & operator<<(istream &is, Integer i) {
     17     is >> i.i;
     18     return is;
     19 } 
     20 Integer operator-(Integer a, Integer b) {
     21     return a.i - b.i;
     22 }
     23 int main() {
     24     Integer i(-1);
     25     Integer j;
     26     cin >> j;
     27     i = -i;
     28     i = i - j;
     29     i = i + 10;
     30     cout << i;
     31 }
   

读程序，写出程序运行的结果

1.    1 #include <iostream>
      2 using namespace std;
      3 int inc( int &a) {
      4     return ++a;
      5 }
      6 int dec( int a) {
      7     return --a;
      8 }
      9 int main() {
     10     int b = 10;
     11     cout << inc(b) << endl;
     12     cout << dec(b) << endl;
     13     cout << inc(b) << endl;
     14 }
   

2.    1 #include <iostream>
      2 #include <string>
      3 using namespace std;
      4 int f( string a );
      5 int f( int b , int c = 1);
      6 int f( bool b);
      7 int main() {
      8     string s = "";
      9     cout << f(s) << endl;
     10     cout << f('\060') << endl;
     11     cout << f(1, 2) << endl;
     12     cout << f(false) << endl;
     13     cout << f(0) << endl;
     14 }
     15 int f( string a) {
     16     return a.length();
     17 }
     18 int f( int b, int c) {
     19     return b * c + b + c + 1;
     20 }
     21 int f(bool b) {
     22     return b?1:-1;
     23 }
   

3.    1 #include <iostream>
      2 using namespace std;
      3 class Z {
      4 public:
      5     Z(int i) : id(i) { cout << id << " created" << endl; }
      6     ~Z() { cout << id << " destroyed" << endl; }
      7     Z(Z &z) : id(z.id) { cout << id << " created a copy" << endl; }
      8 private:
      9     int id;
     10 };
     11 Z z(0);
     12 int main() {
     13     cout << "main start" << endl;
     14     Z z1(1);
     15     Z z2(2);
     16     Z *z3 = new Z(3);
     17     Z z4(z1); 
     18 }
   

4.    1 #include <iostream>
      2 using namespace std;
      3 class X {
      4 public: 
      5     X(int a) : x(a) { cout << "create X:" << x << endl; }
      6     ~X() { cout << "destroy X:"<< x << endl; }
      7 private:
      8     int x;
      9 };
     10 class Y : public X{
     11 public:
     12     Y() : x(1), X(2) { cout << "create Y" << endl; }
     13     ~Y() { cout << "destroy Y" << endl; }
     14 private:
     15     X x;
     16 };
     17 
     18 int main() {
     19     X x(5);
     20     Y  y;
     21 }
   

5.    1 #include <iostream>
      2 using namespace std;
      3 class B{
      4 public:
      5     virtual void f() { cout << "B::f() "; }
      6     void g() { cout << "B::g() "; }
      7     virtual void h() { f(); }    
      8 };
      9 class D : public B {
     10 public:
     11     void f() { cout << "D::f() "; }
     12     void g() { cout << "D::g() "; }
     13 };
     14 int main() {
     15     B b;
     16     b.f(); b.g(); b.h();
     17     cout << endl;
     18     B *p = &b;
     19     p->f(); p->g(); p->h();
     20     cout << endl;
     21     B *p = new D;
     22     p->f(); p->g(); p->h();
     23     cout << endl;
     24     B &r = *p;
     25     r.f(); r.g(); r.h();
     26     cout << endl;
     27     delete p;
     28 }
   

6.    1 #include <iostream>
      2 using namespace std;
      3 class B{
      4 public:
      5     B () { cout << "create B" << endl; }
      6     virtual ~B() { cout << "destroy B" << endl; }
      7     virtual void f() { cout << "B::f()" << endl; }
      8     virtual void f(int a) { cout << "B::f(int)" << endl; }
      9 };
     10 class D : public B {
     11 public:
     12     D() { cout << "create D" << endl; }
     13     virtual ~D() { cout << "destroy  D" << endl; }
     14     virtual void f() { cout << "D::f()" << endl; }
     15     virtual void f(bool a) { cout << "D::f(bool)" << endl; }
     16 };
     17 int main() {
     18     B *p = new B;
     19     p->f();
     20     p->f(0);
     21     delete p;
     22     p = new D;
     23     p->f();
     24     p->f(0);
     25     delete p;
     26     D *d = new D;
     27     d->f();
     28     d->f(0);
     29     delete d;
     30 }
   

7.    1 #include <iostream>
      2 using namespace std;
      3 class D {
      4 public:
      5     D() { cout << "D created" << endl; }
      6     D(D&) { cout << "D created a copy" << endl; }
      7     ~D() { cout << "D destroyed" << endl; }
      8     D& operator=(D&) { cout << "D assigned" << endl; return *this; }
      9     void operator++() { cout << "operator++" << endl; }
     10     void operator++(int) { cout << "operator++ with int" << endl; }
     11 };
     12 int main() {
     13     D d1;
     14     D d2(d1);
     15     d1 = d2;
     16     ++d1;
     17     d2++;
     18 }
   

程序填空题

编程题，按要求编写程序

1. 13.     实现字符串类string，声明如下
   class string {
   public:
           string(const char *str = "");           // 普通构造函数
           string(const string &other);            // 拷贝构造函数
           ~string();                                          // 析构函数
           string & operator = (const string &other);      // 赋值函数
       bool operator==(const string &s);
       bool operator!=(const string &s);
       bool operator<(const string &s);
       bool operator>(const string &s);
       bool operator<=(const string &s);
       bool operator>=(const string &s);
       string operator +(const string &s); //连接
       string operator +=(const string &s);
       int length() const;
       bool empty() const;
           char* c_str()   { return m_data; }
   private:
           char *m_data;                               // 用于保存字符串
   };
   ostream &operator<<(ostream &os, const string &s);
   istream &operator>>(istream &is, string &s);