解析C++例题代码第9章习题1
第9章习题
【例9-1】
//example9_1.cpp
#include
#include
using namespace std;
int main()
{
float a,b,c;
double x1,x2;
cout<<"请输入一元二次方程的系数a、b和c的值:";
cin>>a>>b>>c;
x1=(-b+sqrt(b*b-4*a*c))/(2*a);
x2=(-b-sqrt(b*b-4*a*c))/(2*a);
cout<<"方程的实根是: x1="< cin>>a>>b>>c; try { if(0 == b) throw b;// throw表达式中b并无意义，代表float型即可 if((b*b-4*a*c)<0) throw 1.0;// 1.0本身无实际意义，只是代表double型 x1=(-b+sqrt(b*b-4*a*c))/(2*a); x2=(-b-sqrt(b*b-4*a*c))/(2*a); cout<<"方程的实根是: x1="< } catch(double) //捕获double类型的异常 { cout<<"开方为负值，方程无解!"< } cout<<"程序结束!"< return 0; } 【例9-2】 //example9_2.cpp #include using namespace std; class Stack { public: Stack( int capacity=10 );//建立一个空栈，其最大容量的缺省值为10 ~Stack(){delete[] elements;};//析构函数，释放数组资源 bool push( int value );//压栈操作 bool pop(int &top_value);//出栈操作 bool isfull(){return top < maxsize? false : true;};//判断栈是否满bool isempty(){return top ? false : true;}; //判断栈是否空 int size(){ return top; }//返回栈中元素的个数 void display();//显示栈中的全部元素 private: int top;//栈顶 int * elements;//存放栈中元素的栈数组 int maxsize;//栈可容纳元素的个数 }; Stack:: Stack( int capacity):top(0), maxsize(capacity) { elements = new int[capacity];//动态创建栈数组 } bool Stack::pop( int &top_value ) { if ( isempty() ) return false; //栈空返回false top_value = elements[ --top ]; return true; //出栈操作正常返回true } bool Stack::push( int value ) { if ( isfull() ) return false;//栈满则返回false elements[top++ ] = value; return true; //压栈操作正常返回true } void Stack::display() { if ( !size() ) { cout << "栈中没有元素！\n"; return; } cout << "(栈中有 " << size() << "个元素)( bottom: "; for ( int i = 0; i < top; ++i ) cout << elements[i] << " "; cout << " :top )\n"; } int main() { int i,n; cout << "请输入需要栈的元素个数："; cin >>n; Stack myStack(n); cout << "请输入压栈元素的个数："; cin >>n; for ( i = 1; i <= n; ++i ) myStack.push( i ); myStack.display(); cout << "请输入出栈元素的个数："; cin >>n; for ( i = 1; i <= n; ++i ) { int x; myStack.pop( x ); } myStack.display(); return 0; } 【例9-3】 //example9_3.cpp #include #include #include using namespace std; typedef struct zero//声明除数为零异常类型 {string s;}ZERO; typedef struct negative//声明开方值为负异常类型 {string s;}NEGATIVE; fun2(int a,int b,int c)//抛出异常的函数 { ZERO s1;NEGATIVE s2; s1.s="除数为零";s2.s="开方值为负数"; if(0 == b) throw s1; if((b*b-4*a*c)<0) throw s2; return sqrt(b*b-4*a*c); } fun1(int a,int b,int c) //捕获异常并重新抛出异常 { try { return(-b+fun2(a,b,c))/(2*a); } catch(ZERO) { throw;//重新抛出异常 } } int main() { float a,b,c; cout<<"请输入一元二次方程的系数abc:"; cin>>a>>b>>c; try { cout<<"方程的一个实根是: x1="< } catch(ZERO S1) //捕获除数为零异常,并处理异常 { cout< } catch(NEGATIVE S2)// 捕获开方值为负数异常,并处理异常 { cout< } cout<<"程序结束!"< return 0; } 【例9-4】 //example9_4.cpp #include using namespace std; void Fun( void ); class intArray { public: intArray (int n) { p = new int[ n ]; cout << "构造intArray，分配具有" < } ~intArray () { delete[] p; cout << "析构intArray，释放资源。" << endl; } private: int *p; }; void Fun() { intArray ia(10); cout<< "在Fun()中抛掷整型异常。" << endl; throw 1; } int main() { try { cout << "在主函数的try块中调用函数Fun()。" << endl; Fun(); } catch( int ) { cout << "在主函数catch子句捕获到整型异常," ; cout << "并进行异常处理。"<< endl; } cout << "程序结束!" << endl; return 0; } 【例9-5】 //example9_5.cpp #include #include using namespace std; class Excp//声明异常基类 { public: static void print( string msg )// 打印错误信息 { cout< } }; class pushOnFull : public Excp//声明栈满异常类 { public: pushOnFull( int i ) : tempvalue( i ) { } int getTempValue() { return tempvalue; } private: int tempvalue;//存放异常发生时没有压栈的值 }; class popOnEmpty : public Excp //声明栈空异常类 { }; class newError : public Excp//声明动态分配内存异常类 { }; class otherError : public Excp//声明其它异常类 { }; class Stack { public: Stack( int capacity=10 ) throw (newError);//建立一空栈，其容量的缺省值为10 ~Stack(){delete[] elements;};//析构函数，释放数组资源 void push( int value ) throw (pushOnFull);//压栈 void pop(int &top_value) throw (popOnEmpty);//出栈 bool isfull(){return top < maxsize? false : true;}; bool isempty(){return top ? false : true;}; int size(){ return top; } void display(); private: int top;//栈顶指针 int * elements;//存放栈中元素的栈数组 int maxsize;//栈可容纳元素的个数 }; Stack:: Stack( int capacity):top(0), maxsize(capacity) { elements = new int[capacity];//动态创建栈数组 if(0==elements) throw newError();//如果分配失败，抛出异常} void Stack::pop( int &top_value ) { if ( isempty() ) throw popOnEmpty();//栈空，则抛出异常 top_value = elements[ --top ]; } void Stack::push( int value ) { if( isfull() ) throw pushOnFull(value);//栈满抛出异常，并将未入栈元素值传送给异常处理 elements[top++ ] = value; } void Stack::display() { if ( !size() ) { cout << "栈中已没有元素！\n"; return; } cout << "(栈中有 " << size() << "个元素)(bottom: "; for( int i = 0; i < top; ++i ) cout << elements[i] << " "; cout << ":top)\n"; } int main() { int i,n,count; try { cout << "请输入需要栈的元素个数："; cin >>n; Stack myStack(n); cout << "请输入压栈元素的个数："; cin >>n; for ( i = 1; i <= n; count=++i ) myStack.push( i ); myStack.display(); cout << "请输入出栈元素的个数："; cin >>n; for ( i = 1; i <= n; count=i++ ) { int x; myStack.pop( x ); } cout << "已出栈"< } catch(pushOnFull e) { e.print("栈已满！"); cout << "栈中有"< cout << "值为"< } catch(newError) { newError::print("给栈分配空间时出错！"); } catch(popOnEmpty) { cout << "已出栈"< popOnEmpty::print("栈已空！"); } catch(Excp) { Excp::print("程序其它异常在此处理！"); } return 0; } 【例9-6】 //example9_6.cpp #include #include #include using namespace std; class Array { public: Array(const char *source, int sz) { size = sz; ca = new char[size]; for ( int i = 0; i < size; ++i ) if ( !source ) ca[i] = 0; else ca[i] = source[i]; } char &operator[]( int i ) const { if ( i < 0 || i >= size ) { string es ="数组越界！"; throw out_of_range( es ); //将es字符串传给out_of_range对象。 } return ca[i]; } private: int size;char *ca; }; int main() { try { char ca[] = { 'A','B','C','D','E','F'}; Array CA( ca, sizeof(ca)/sizeof(char) );//实例化一个字符数组类 CA[5]='X';//正常访问字符数组类 CA[6]='G';//越界访问数组类将引发异常 return 0; } catch ( const out_of_range &excp ) { cout<< excp.what()< return -1; } } 【例9-7】 //example9_7.cpp #include using namespace std; int main() { int num; cout<< "请输入一个整数（0退出）： "; try { while (1) { cin>>num; if (0 == num) throw 1; //退出循环 cout<< "你输入了整数: " << num << "\n请输入下一个数（0退出）： " ; } } catch (int ) { cout<< "程序结束！" < } return 0; } 【例9-8】 //example9_8.cpp #include #include using namespace std; class A { public: A() { cout<<"构造函数执行。"< cout<<"抛出整型异常。"< throw 1; } ~A() { cout<<"析构函数执行。"< } }; int main() { try { A *a=new A; delete a; } catch(int) { cout<<"异常处理！"< return 0; } 【例9-9】 //example9_9.cpp #include #include using namespace std; class B { public: ~B() { cout<<"析构函数被调用。\n"; cout<<"析构函数抛出异常。\n"; throw 1; } void *operator new(size_t n) throw() { cout<<"new运算符被调用。\n"; return malloc(n); } void operator delete(void *p) throw() { cout<<"delete运算符被调用。\n"; if (p != NULL) free(p); } }; int main() { B *b = new B; try { delete b; } catch(int) { cout<<"异常处理！\n"; } return 0; } 【例9-10】 //example9_10.cpp #include #include #include using namespace std; typedef struct student { int num; char name[20]; float score; }Student; class StudentArray { public: StudentArray(int n) { capacity=n; stud = new Student[capacity]; if(0==stud) throw bad_alloc();//抛出内存分配异常 } ~StudentArray() { delete[] stud; } void DataInput() void FileInput() throw (ios_base::failure); //抛出异常的声明 void FileOutput() throw (ios_base::failure); private: Student *stud; int capacity; }; void StudentArray::DataInput()//从键盘输入学生的数据 { cout<<"请按学号、姓名、成绩依次输入"< for(int i=0;i cin>>stud[i].num>>stud[i].name>>stud[i].score; } void StudentArray::FileInput() { int i; ifstream infile("student.dat",ios::binary); if(!infile) { string es ="从文件读数据错！"; throw ios_base::failure( es ); } for(i=0;i infile.close();//关闭文件 float sum=0; for(i=0;i sum=sum+stud[i].score; cout<<"学生的平均成绩是："< void StudentArray::FileOutput() { ofstream outfile("student.dat",ios::binary); if(!outfile) { string es ="向文件写数据错！"; throw ios_base::failure( es ); } for(int i=0;i outfile.close();//关闭文件 } int main() { int n; cout<<"请输入学生人数："; cin>>n; try { StudentArray studarr(n); studarr.DataInput(); studarr.FileOutput(); studarr.FileInput(); } catch(ios_base::failure &excp) { cout< return -1; } catch(bad_alloc &excp) { cout< return -1; } return 0; }