C++练习题2015年下(读程序练习题)

一、读程序题目1.本题考核指针与字符串，指向字符串的指针，意味着指针变量中存放字符串在内存中所占存储空间的首地址。

此时指针变量可以作为数组名来使用。

#include<iostream >using namespace std;void main(){char *str = "abbcdace";int c1 = 0, c2 = 0, c3 = 0, c4 = 0;for (int i = 0; str[i]; i++)switch (str[i]){default: c4++;case'a':c1++;case'b':c3++;case'c':c2++;}cout << c1 << "," << c2 << "," << c3 << "," << c4 << endl;}◎知识点复习：字符串结束标记为\0 ,字符串在内存中存放时实际字符后存放\0这个标记。

当输出字符串时遇到\0停止输出。

◎ for(int i = 0; str[i]; i++) 中的str[i]表示循环条件，读出字符数组str中的各个字符，显然遇到\0停止。

即str[i]等价于str[i]!=’\0’。

◎ Switch结构特点：找到表达式满足的入口后开始执行本分支中的语句，遇到 break语句跳出switch结构，但如果没有遇到break，执行完本分支后继续执行下一分支语句。

◎将switch结构改为如下形式，结果是什么？switch (str[i]){default: c4++; break;case'a':c1++; break;case'b':c3++; break;case'c':c2++; break;}2.枚举类型与枚举变量的定义enum 枚举类型名{枚举常量列表} [变量列表] ;※定义枚举类型的同时定义枚举变量：enum Color { Red, Yellow, White, Blue, Black}c1;※先定义类型，再定义变量：#include<iostream>using namespace std;enum Color{ Red, Yellow, White, Blue, Black}c;void main(){c= Red; cout << c << endl;c = Yellow; cout << c << endl;c = Black; cout << c << endl;}第一行运行结果为? 第二行运行结果为？第三行运行结果为？3.复合语句：在复合语句中定义的变量仅在该语句中有效。

#include<iostream >using namespace std;int c = 0;class Base{int a;public:Base(){a = 2;c++;}~Base() { c--; }friend void show();};void show() { cout << "结果为： " << c << endl; }void main(){Base a;show();{ Base b[3];show();}show();}4.继承，组合#include<iostream >using namespace std;class Base{int x;public:Base(int y){ cout << "调用基类构造函数" << endl; x=y; }~Base(){ cout << "调用基类析构函数" << endl; }void showx(){ cout << x << ","; }int Getx(){ return x; }};class Derived :public Base{int k;Base b1;public:Derived(int n, int m, int p) :Base(m), b1(p){cout << "调用派生类构造函数" << endl;k= n;}~Derived(){ cout << "调用派生类析构函数" << endl; }void show(){Base::showx();cout << k << "," << b1.Getx() << endl;}};void main(){Derived obj(8, 13, 24);obj.show();}5.函数#include<iostream >using namespace std;class Test{public:Test(double m, double n, double d) :p(d) { a = m; b = n; } void Show();void Show() const;private:double a, b;const double p;};void Test::Show(){cout << a << "," << b << endl;cout << "p=" << p << endl;}void Test::Show() const{cout << a<< "," << b << " const" << endl;cout << "p=" << p << " const" << endl;}void main(){Test t1(3.3, 5.5, 7.7);t1.Show();const Test t2(8, 6, 4);t2.Show();}6.指针#include<iostream >using namespace std;void fun1(int a, int *p1, int *p2){*p1 = 2*a;*p2 = a*a;}void main(){int a, p, q;a = 5;fun1(a, &p, &q);cout << p << "," << q << endl;}7.联合#include<iostream >using namespace std;union data{int i;char c;float f;}d;void main(){for (int j = 0; j<3; j++)switch (j){case 0: d.i = 8; cout << d.i << endl; break;case 1: d.c = 'a'; cout << d.c << endl; break;case 2: d.f = 9.1; cout << d.f << endl; break;}}8.运算符重载#include<iostream >#include<string>using namespace std;class Point{public:Point(char *s){p = new char[strlen(s) + 1];strcpy(p, s);}void Show() { cout << p << endl; }char& operator [](int i) { return *(p + i); } private:char *p;};void main(){char *s = "PEKING";Point x(s);x.Show();int n = strlen(s);while (n >= 0){x[n - 1] = x[n - 1] + 32;n--;}x.Show();}9.多重继承与虚函数#include<iostream>using namespace std;class A {public:virtual void fun(){cout << "fun in class A" << endl;}};class B{public:virtual void fun(){cout << "fun in class B" << endl;}};class C :public A, public B{public:void fun(){cout << "fun in class C" << endl;}};int main(){C c;A& p1 = c;B& p2 = c;C& p3 = c;p1.fun();p2.fun();p3.fun();}10. 纯虚函数（抽象类），基类指针指向派生类对象。

#include<iostream>#include<string>using namespace std;class Vehicle{public:virtual void show() = 0;protected:char Name[20];};class Car :public Vehicle{public:Car(char *name){strcpy(Name, name);}void show(){cout << Name << endl;}protected:int Radius;};class Truck :public Vehicle{public:Truck(char *name){strcpy(Name, name);}void show(){cout << Name << endl;}};class Boat :public Vehicle{public:Boat(char *name){strcpy(Name, name);}void show(){cout << Name << endl;}};void main(){Vehicle *p;Car car("法拉利");Truck truck("卡车");Boat boat("潜水艇");p = &car;p->show();p = &truck;p->show();p = &boat;p->show();}11. 异常处理机制读懂程序9-1，9-2。