C++学习之路 day3

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Day3知识点：

1.类的创建实例

例1.C中闰年的判断

//date.h#ifndef DATE_H#define DATE_Hstruct Date{    int year;    int month;    int day;};void init(Date & a);void print(Date & a);bool isLeapYear(Date & a);#endif // DATE_H

//date.cpp#include "date.h"#include <iostream>using namespace std;void init(Date & a){    cin >> a.year >> a.month >> a.day;}void print(Date & a){    cout<<"year: "<<a.year<<" month: "<<a.month<<" day: "<<a.day<<endl;}bool isLeapYear(Date & a){    if ((!(a.year % 4) && a.year % 100) || !(a.year % 400))        return true;    else        return false;}

//main.cpp#include<iostream>#include"date.h"using namespace std;int main(int argc,int * argv[]){    Date a;    init(a);    print(a);//    a.year = 1999;    //可以在此改变结构体中的值    if (isLeapYear(a))    {        cout << a.year <<" is a leap year! "<< endl;    }    else    {        cout << a.year << " is not a leap year! " << endl;    }    return 0;}

例2.C++中利用类的成员函数闰年的判断

//date.h#ifndef DATE_H#define DATE_Hclass Date{public:    void init();    void print();    bool isLeapYear();    int get_year();private:    int year;    int month;    int day;};#endif // DATE_H

//date.cpp#include "date.h"#include <iostream>using namespace std;void Date::init(){    cin >>year >>month >>day;}void Date::print(){    cout<<"year: "<<year<<" month: "<<month<<" day: "<<day<<endl;}bool Date::isLeapYear(){    if ((!(year % 4) && year % 100) || !(year % 400))        return true;    else        return false;}int Date::get_year(){    return year;}

//main.cpp#include<iostream>#include"date.h"using namespace std;int main(int argc,int * argv[]){    Date a;    a.init();    a.print();    if (a.isLeapYear())    {        cout << a.get_year() <<" is a leap year! "<< endl;    }    else    {        cout << a.get_year() << " is not a leap year! " << endl;    }    return 0;}

2. constructor:构造器：

1）与类名相同，无返回，被系统生成对象时自动调用，用于初始化。

2）可以有参数，默认参数，可以重载，重载和默认不能同时使用，包含标配，为了对象的无参创建。

3）若未提供任何构造，系统默认生成一个无参构造器。

#include <iostream>#include<string.h>using namespace std;class Stu{public:    Stu(string na)        :len(strlen(na.c_str())),name(na)    {    }    void dis()    {        cout<<len<<endl;    }private:    int len;    string name;};int main(){    Stu s("china");    s.dis();    return 0;}

例3.已定义栈空间(无构造函数)的堆栈弹栈模拟

//stack.h#ifndef STACK_H#define STACK_Hclass Stack{public:     void init();     bool isEmpty();     bool isFull();     char push(char c);     void pop();private:    char space[1000];    int top = 0;};#endif // STACK_H

//stack.cpp#include "stack.h"#include<iostream>#include<string.h>using namespace std;void Stack::init(){    top = 0;    memset(space,0,1024);}bool Stack::isEmpty(){    return top == 0;}bool Stack::isFull(){    return top == 1024;}char Stack::push(char c){    space[top++] = c;}void Stack::pop(){    cout<<space[--top]<<endl;}

//main.cpp#include <iostream>#include "stack.h"using namespace std;int main(int argc, char *argv[]){    Stack a;//    if(!(a.isFull()))//        a.push('a');//    if(!(a.isFull()))//        a.push('b');//    if(!(a.isFull()))//        a.push('c');//    if(!(a.isFull()))//        a.push('d');//    if(!(a.isFull()))//        a.push('e');//    if(!(a.isFull()))//        a.push('f');//    if(!(a.isFull()))//        a.push('g');    for(char c='a';(c<='z')&&(!a.isFull());c++)        a.push(c);    for(;!(a.isEmpty());)        a.pop();    return 0;}

例4.自定义栈空间的堆栈弹栈模拟

//stack.h#ifndef STACK_H#define STACK_Hclass Stack{public:    Stack(int size = 1024)    {        top = 0;        space = new char[size];        _size = size;    }     void init();     bool isEmpty();     bool isFull();     char push(char c);     void pop();private:    char *space;    int top = 0;    int _size;};#endif // STACK_H

//stack.cpp#include "stack.h"#include<iostream>#include<string.h>using namespace std;void Stack::init(){    top = 0;    memset(space,0,_size);}bool Stack::isEmpty(){    return top == 0;}bool Stack::isFull(){    return top == _size;}char Stack::push(char c){    space[top++] = c;}void Stack::pop(){    cout<<space[--top]<<endl;}

//main.cpp#include <iostream>#include "stack.h"using namespace std;int main(int argc, char *argv[]){    Stack a(15);    for(char c='a';(c<='z')&&(!a.isFull());c++)        a.push(c);    for(;!(a.isEmpty());)        a.pop();    return 0;}

3. destructor:析构器

1） 与类名相同（前面加~，如~Stack(){}），无参(不能重载)，无返回。

2）对象消失的时候自动被调用用于对象销毁之前的内存处理工作。

3）若未提供，系统默认生成一个空析构器。

4）在两种情况下被调用：1.栈对象离开作用域；2.堆对象被delete

#include <iostream>using namespace std;class Stu{public:    Stu()    {        name = new char[100];    }    ~Stu()    {        delete name;    }private:    int a;    char* name;};int main(int argc, char *argv[]){    Stu* s = new Stu;    delete s;    return 0;}

例5.不带构造函数与析构函数的链表的创建

#include <iostream>using namespace std;struct Node{    char data;    struct Node* next;};class List{public:    List * createList();    //用于给head初始化    void insertList(char d);    void traverseList();private:    Node * head;};List * List::createList(){    head = new Node;    head->next = NULL;}void  List::insertList(char d){    Node* cur = new Node;    cur->data = d;    cur->next = head->next; //链表逆序    head->next = cur;}void  List::traverseList(){    Node* ph = head->next;    while(ph != NULL)    {        cout<<ph->data<<endl;        ph = ph->next;    }}int main(int argc, char *argv[]){    List list;    list.createList();    for(char i = 'a';i<='z';i++)        list.insertList(i);    list.traverseList();    return 0;}

例6.带构造析构函数的链表创建

//myList.h#ifndef MYLIST_H#define MYLIST_Hstruct node{    int data;    struct node* next;};class myList{public:    myList();    ~myList();    void createList();    void insertList(int d);    void traverseList();private:    struct node* head;};#endif // MYLIST_H

//mylist.cpp#include "mylist.h"#include<stdio.h>#include<iostream>using namespace std;myList::myList(){    head = new node;    head->next = NULL;}myList::~myList(){    node* t = head;    while(head)    {//        t = head->next;//        delete head;//        head = t;        t = head;        head = head->next;        delete t;    }}void myList::insertList(int d){    node* insert = new node;    insert->data = d;    insert->next = head->next;    head->next = insert;}void myList::traverseList(){    node *ph = head->next;    while(ph != NULL)    {        cout<<ph->data<<endl;        ph = ph->next;    }}

//main.cpp#include <iostream>#include "mylist.h"using namespace std;int main(){    myList list;    list.insertList(1);    list.insertList(2);    list.insertList(3);    list.insertList(4);    list.insertList(6);    list.traverseList();    return 0;}

4.在构造类时通常情况下无参构造器要包含在内，在提供了默认参数或重载时时可以不包含,其中用默认比较好，默认参数只能用在声明中。

A(){};//可省略A(int i = 0,int j = 0,int k = 0):x(i),y(j),z(k){};

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