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C++基础知识

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我是靠谱客的博主 甜美流沙，最近开发中收集的这篇文章主要介绍C++基础知识，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

1.一个整数以8、10、16进制输出：

   一个布尔类型：

#include <iostream>    //输入输出头文件
#include <stdlib.h>    //标准库头文件
using namespace std;
int main() 
{
	cout << "int:" << endl;
	int x = 0;
	cin >> x;
	cout << oct << x << endl;
	cout << dec << x << endl;
	cout << hex << x << endl;

	cout << "bool:" << endl;
	bool flag = false;
	cin >> flag;
	cout << boolalpha << flag << endl;
	system("pause");
	return 0;
}

//命名空间关键子 namespace

namespace A {
	int x = 0;
	void f1();
	void f2();
}
namespace B {
	int x = 2;
	void f1();
	void f3();
}
cout << A::x << endl;
B::f1();
#include <iostream>
#include <stdlib.h>

namespace A 
{
	int X = 0;
	void fun() 
	{
		std::cout << "A" << std::endl;
	}
	void fun1() 
	{
		std::cout << "1A" << std::endl;
	}
}
namespace B
{
	int X = 2;
	void fun()
	{
		std::cout << "B" << std::endl;
	}
	void fun2()
	{
		std::cout << "2B" << std::endl;
	}
}

using namespace B;
int main() 
{
	std::cout << A::X << std::endl;
	A::fun();
	fun();
	A::fun1();
	B::fun2();
	fun2();
	system("pause");
	return 0;
}

2.通过栈实例化对象和通过堆实例化对象：

通过栈实例化对象代码：

通过堆实例化对象代码：

#include <iostream>
#include <stdlib.h>
using namespace std;

class Coordinate
{
public:
	int x = 1, y = 2;
	void PrintX()
	{
		cout << x << endl;
	}
	void PrintY()
	{
		cout << y << endl;
	}
};

int main()
{
	Coordinate coor;//使用栈实例化对象
	coor.x = 10;
	coor.y = 20;
	coor.PrintX();
	coor.PrintY();

	Coordinate *p=new Coordinate();//使用堆实例化对象
	if (NULL == p)
	{
		return 0;
	}

	p->x = 100;
	p->y = 200;
	p->PrintX();
	p->PrintY();
	delete p;
        p = NULL;
	system("pause");
	return 0;
}

3.C++获取字符串输入：

	cout << "请输入姓名：";
	string name;
	getline(cin, name);

4.为什么c++类的定义中成员名习惯加"m_"?

m是member的缩写，表示这是成员名。

2dx里大量使用了这个 不过3.0里取消了 现在直接是  _xxx

满屏幕的m_ 看着真恶心那

5.内联函数

同文件类外定义：

//同文件类外定义
#include <iostream>
#include <string>
#include <stdlib.h>
using namespace std;

class Teacher
{
public:
	void SetName(string);
	string GetName();
	void SetAge(int _age);
	int GetAge();
	void SetGender(string _gender);
	string GetGender();
	void Teach();

private:
	string strName;
	int iAge;
	string strGender;
};

void Teacher::SetName(string _name)
{
	strName = _name;
}
string Teacher::GetName()
{
	return strName;
}
void Teacher::SetAge(int _age)
{
	iAge = _age;
}
int Teacher::GetAge()
{
	return iAge;
}
void Teacher::SetGender(string _gender)
{
	strGender = _gender;
}
string Teacher::GetGender()
{
	return strGender;
}
void Teacher::Teach()
{
	cout << "正在上课" << endl;
}

int main()
{
	Teacher *teacher = new Teacher();
	teacher->SetName("kerven");
	teacher->SetAge(23);
	teacher->SetGender("男");
	cout << "姓名：" + teacher->GetName() << endl;
	cout << "年龄：" << teacher->GetAge() << endl;
	cout << "性别：" + teacher->GetGender() << endl;
	teacher->Teach();

	delete teacher;
	teacher = NULL;
	system("pause");
	return 0;
}

分文件类外定义：

Teacher.h
//分文件类外定义
#include <string>
using namespace std;
class Teacher
{
public:
	void SetName(string _name);
	string GetName();
	void SetAge(int _age);
	int GetAge();
	void SetGender(string _gender);
	string GetGender();
	void Teach();

private:
	string strName;
	int iAge;
	string strGender;
};
Teacher.cpp
//分文件类外定义
#include "Teacher.h"
#include <iostream>
using namespace std;

void Teacher::SetName(string _name)
{
	strName = _name;
}
string Teacher::GetName()
{
	return strName;
}
void Teacher::SetAge(int _age)
{
	iAge = _age;
}
int Teacher::GetAge()
{
	return iAge;
}
void Teacher::SetGender(string _gender)
{
	strGender = _gender;
}
string Teacher::GetGender()
{
	return strGender;
}
void Teacher::Teach()
{
	cout << "正在上课" << endl;
}
//分文件类外定义
#include <iostream>
#include <string>
#include "Teacher.h"
#include <stdlib.h>
using namespace std;

int main()
{
	Teacher *teacher = new Teacher();
	teacher->SetName("kerven");
	teacher->SetAge(23);
	teacher->SetGender("男");
	cout << "姓名：" + teacher->GetName() << endl;
	cout << "年龄：" << teacher->GetAge() << endl;
	cout << "性别：" + teacher->GetGender() << endl;
	teacher->Teach();

	delete teacher;
	teacher = NULL;
	system("pause");
	return 0;
}

6.内存分区

7.C++构造函数初始化列表初始化列表的特性：--效率高、速度快

(1).初始化列表先于构造函数执行

(2).初始化列表只能用于构造函数

(3).初始化列表可以同时初始化多个数据成员

//初始化列表存在的必要性
class Circle
{
public:
	Circle():dPi(3.14){}

private:
	const double dPi;
};

8.C++拷贝构造函数--拷贝构造函数不能被重载

    Teacher t1;
    Teacher t2 = t1;
    Teacher t3(t1);

9.析构函数

10.C++引用（别名）

 

11.C++语言-const（常量）

常指针、指针常量、常量常指针

12.

13.C++ 忽略警告的写法：

#pragma warning(disable:4305)

14.对象含有对象成员时各构造函数与析构函数的执行顺序：

例子：当线段Line含有坐标A和B时，

构造函数：A、B、Line

析构函数：Line、B、A

15.[C++]深拷贝与浅拷贝

 

16.C++ sort函数

#include <algorithm>

sort(a1, a1 + size);

17.C++动态数组

#include <iostream>

int main() {
    // 1. initialize
    vector<int> v0;
    vector<int> v1(5, 0);
    // 2. make a copy
    vector<int> v2(v1.begin(), v1.end());
    vector<int> v3(v2);
    // 2. cast an array to a vector
    int a[5] = {0, 1, 2, 3, 4};
    vector<int> v4(a, *(&a + 1));
    // 3. get length
    cout << "The size of v4 is: " << v4.size() << endl;
    // 4. access element
    cout << "The first element in v4 is: " << v4[0] << endl;
    // 5. iterate the vector
    cout << "[Version 1] The contents of v4 are:";
    for (int i = 0; i < v4.size(); ++i) {
        cout << " " << v4[i];
    }
    cout << endl;
    cout << "[Version 2] The contents of v4 are:";
    for (int& item : v4) {
        cout << " " << item;
    }
    cout << endl;
    cout << "[Version 3] The contents of v4 are:";
    for (auto item = v4.begin(); item != v4.end(); ++item) {
        cout << " " << *item;
    }
    cout << endl;
    // 6. modify element
    v4[0] = 5;
    // 7. sort
    sort(v4.begin(), v4.end());
    // 8. add new element at the end of the vector
    v4.push_back(-1);
    // 9. delete the last element
    v4.pop_back();
}

18.C++虚继承

19.

#ifndef PERSON_H

#define PERSON_H

#endif

20.来一次完整的：

//Person.h
#ifndef PERSON_H
#define PERSON_H
#include <iostream>
using namespace std;

class Person
{
public:
	Person(string name);
	virtual ~Person() {}
	virtual void work() = 0;

private:
	string strName;
};
#endif
//Person.cpp
#include "Person.h"

Person::Person(string name)
{
	strName = name;
}
//Worker.h
#ifndef WORKER_H
#define WORKER_H

#include "Person.h"
class Worker : public Person
{
public:
	Worker(string name, int age);
	virtual void work();

private:
	int iAge;
};
#endif

//Worker.cpp
#include <iostream>
#include "Worker.h"
using namespace std;

Worker::Worker(string name, int age) : Person(name)
{
	iAge = age;
}
void Worker::work()
{
	cout << "work" << endl;
}
//Dustman.h
#ifndef DUSTMAN_H
#define DUSTMAN_H
#include "Worker.h"
class Dustman:public Worker
{
public:
	Dustman(string name, int age);
	virtual void work();
};
#endif

//Dustman.cpp
#include "Dustman.h"
#include <iostream>
using namespace std;

Dustman::Dustman(string name, int age) :Worker(name, age)
{

}
void Dustman::work()
{
	cout << "扫地" << endl;
}
//Demo.cpp
#include "Person.h"
#include "Worker.h"
#include "Dustman.h"
using namespace std;

int main()
{
	Dustman *d = new Dustman("kerven", 18);
	d->work();

	Worker worker("xiaowen", 20);
	worker.work();

	delete d;
	d = NULL;
	system("pause");
	return 0;
}

NEW

========C++常用标准库：vector、map、list

vector向量：对数组的封装

特点：读取能在常数时间内完成

vector<T> v1;        --vector<int> ivec1;   --vector<string> svec1;

vector<T> v2(v1);   --vector<int> ivec2(ivec1);  --vector<string> svec2(svec1);

vector<T> v3(n,i); //v3包含n个值为i的元素 --vector<int> ivec4(10, -1);

vector<T> v4(n); //v4包含n个值 --vector<string> scec(10, "hi");

vector常用函数

迭代器：iterator

#include <iostream>
#include <vector>
using namespace std;

int main()
{
    vector<string> vec;
    vec.push_back("001");
    vector<string>::iterator citer = vec.begin();
    for(;citer!=vec.end();citer++)
    {
        cout << *citer << endl;
    }

    return 0;
}

list:链表（头节点、链表与数组的插入对比、数据域、指针域）--双链表

特点：数据插入速度快

map:映射

#include <iostream>
#include <map>
using namespace std;

int main()
{
    map<int, string> m;
	pair<int, string> p1(10, "shanghai");
	pair<int, string> p2(20, "beijing");
	m.insert(p1);
	m.insert(p2);
	cout << m[10] <<endl;
	cout << m[20] <<endl;

    return 0;
}
#include <iostream>
#include <vector>
#include <list>
#include <string>
#include <map>
using namespace std;

int main()
{
	map<string, string> sTosMap;
	pair<string, string> p1("S", "Shanghai");
	pair<string, string> p2("B", "Beijing");
	sTosMap.insert(p1);
	sTosMap.insert(p2);
	cout << sTosMap["S"] << endl;

	system("pause");
	return 0;
}

数据结构：是指相互之间存在一种或者多种特定关系的数据元素的集合。

队列：先进先出：FIFO:first in first out

普通队列、环形队列

//MyQueue.h
#pragma once
class MyQueue
{
public:
	MyQueue(int queueCapacity);	//InitQueue(&Q) 创建队列
	virtual ~MyQueue();			//DestoryQueue(&Q) 销毁队列
	void ClearQueue();			//ClearQueue(&Q) 清空队列
	bool QueueEmpty() const;	//QueueEmpty(Q) 判空队列
	bool QueueFull()  const;	//判断队列是否为满
	int QueueLength() const;	//QueueLength(Q) 队列长度
	bool EnQueue(int element);	//EnQueue(&Q, element) 新元素入队
	bool DeQueue(int &element); //DeQueue(&Q, &element) 首元素出队
	void QueueTraverse();		//QueueTraverse(Q, visit()) 遍历队列
private:
	int *m_pQueue;				//队列数组指针
	int m_iQueueLen;			//队列元素个数
	int m_iQueueCapacity;		//队列数组容量
	int m_iHead;
	int m_iTail;
};
//MyQueue.cpp

#include "MyQueue.h"
#include <iostream>
using namespace std;

MyQueue::MyQueue(int queueCapacity)
{
	m_iQueueCapacity = queueCapacity;
	m_pQueue = new int[m_iQueueCapacity];
	ClearQueue();
}

MyQueue::~MyQueue()
{
	delete[] m_pQueue;
	m_pQueue = NULL;
}

void MyQueue::ClearQueue()
{
	m_iHead = 0;
	m_iTail = 0;
	m_iQueueLen = 0;
}

bool MyQueue::QueueEmpty() const
{
	return m_iQueueLen == 0 ? true : false;
}

int MyQueue::QueueLength() const
{
	return m_iQueueLen;
}

bool MyQueue::QueueFull() const
{
	return m_iQueueLen == m_iQueueCapacity ? true : false;
}

bool MyQueue::EnQueue(int element)
{
	if (QueueFull())
	{
		return false;
	}
	else 
	{
		m_pQueue[m_iTail] = element;
		m_iTail++;
		m_iTail = m_iTail % m_iQueueCapacity;
		m_iQueueLen++;
		return true;
	}
}

bool MyQueue::DeQueue(int &element)
{
	if (QueueEmpty())
	{
		return false;
	} 
	else
	{
		element = m_pQueue[m_iHead];
		m_iHead++;
		m_iHead = m_iHead % m_iQueueCapacity;
		m_iQueueLen--;
		return true;
	}
}

void MyQueue::QueueTraverse()
{
	for (int i = m_iHead; i < m_iQueueLen + m_iHead; i++)
	{
		cout << m_pQueue[i % m_iQueueCapacity] << endl;
	}
}
//Main.h
//环形队列C++实现
#include <iostream>
#include "MyQueue.h"
using namespace std;

int main()
{
	MyQueue *p = new MyQueue(4);

	p->EnQueue(10);
	p->EnQueue(13);
	p->EnQueue(15);
	p->EnQueue(17);
	p->EnQueue(21);
	p->QueueTraverse();

	int e = 0;
	p->DeQueue(e);
	cout << endl;
	cout << e << endl;

	p->DeQueue(e);
	cout << endl;
	cout << e << endl;

	cout << endl;
	p->QueueTraverse();

	p->ClearQueue();
	p->QueueTraverse();

	cout << endl;

	p->EnQueue(17);
	p->EnQueue(21);
	p->QueueTraverse();

	delete p;
	system("pause");
	return 0;
}

例子：用环形队列，以雇员的类为例子的代码：

//Customer.h
#ifndef CUSTOMER_H
#define CUSTOMER_H

#include <string>
using namespace std;

class Customer
{
public:
	Customer(string name = "", int age = 0);
	void printInfo() const;

private:
	string m_strName;
	int m_iAge;
};

#endif

//Customer.cpp
#include <iostream>
#include "Customer.h"
using namespace std;

Customer::Customer(string name, int age)
{
	m_strName = name;
	m_iAge = age;
}

void Customer::printInfo() const
{
	cout << "xingming:" << m_strName << endl;
	cout << "nianlin:" << m_iAge << endl;
	cout << endl;
}
//MyQueue.h
#pragma once

#include "Customer.h"

class MyQueue
{
public:
	MyQueue(int queueCapacity);	//InitQueue(&Q) 创建队列
	virtual ~MyQueue();			//DestoryQueue(&Q) 销毁队列
	void ClearQueue();			//ClearQueue(&Q) 清空队列
	bool QueueEmpty() const;	//QueueEmpty(Q) 判空队列
	bool QueueFull()  const;	//判断队列是否为满
	int QueueLength() const;	//QueueLength(Q) 队列长度
	bool EnQueue(Customer element);	//EnQueue(&Q, element) 新元素入队
	bool DeQueue(Customer &element); //DeQueue(&Q, &element) 首元素出队
	void QueueTraverse();		//QueueTraverse(Q, visit()) 遍历队列
private:
	Customer *m_pQueue;				//队列数组指针
	int m_iQueueLen;			//队列元素个数
	int m_iQueueCapacity;		//队列数组容量
	int m_iHead;
	int m_iTail;
};
//MyQueue.cpp
#include "MyQueue.h"
#include "Customer.h"
#include <iostream>
using namespace std;

MyQueue::MyQueue(int queueCapacity)
{
	m_iQueueCapacity = queueCapacity;
	m_pQueue = new Customer[m_iQueueCapacity];
	ClearQueue();
}

MyQueue::~MyQueue()
{
	delete[] m_pQueue;
	m_pQueue = NULL;
}

void MyQueue::ClearQueue()
{
	m_iHead = 0;
	m_iTail = 0;
	m_iQueueLen = 0;
}

bool MyQueue::QueueEmpty() const
{
	return m_iQueueLen == 0 ? true : false;
}

int MyQueue::QueueLength() const
{
	return m_iQueueLen;
}

bool MyQueue::QueueFull() const
{
	return m_iQueueLen == m_iQueueCapacity ? true : false;
}

bool MyQueue::EnQueue(Customer element)
{
	if (QueueFull())
	{
		return false;
	}
	else 
	{
		m_pQueue[m_iTail] = element;
		m_iTail++;
		m_iTail = m_iTail % m_iQueueCapacity;
		m_iQueueLen++;
		return true;
	}
}

bool MyQueue::DeQueue(Customer &element)
{
	if (QueueEmpty())
	{
		return false;
	} 
	else
	{
		element = m_pQueue[m_iHead];
		m_iHead++;
		m_iHead = m_iHead % m_iQueueCapacity;
		m_iQueueLen--;
		return true;
	}
}

void MyQueue::QueueTraverse()
{
	for (int i = m_iHead; i < m_iQueueLen + m_iHead; i++)
	{
		m_pQueue[i % m_iQueueCapacity].printInfo();
	}
}
//Main.cpp
//环形队列C++实现
#include <iostream>
#include "MyQueue.h"
using namespace std;

int main()
{
	Customer c1("123", 10);
	Customer c2("456", 20);

	MyQueue *p = new MyQueue(4);
	p->EnQueue(c1);
	p->EnQueue(c2);
	p->EnQueue(c1);
	p->EnQueue(c2);

	p->QueueTraverse();

	Customer cc;
	p->DeQueue(cc);

	p->QueueTraverse();

	delete p;
	system("pause");
	return 0;
}

 

 

 

 

 

 


 

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