堆
- C++对malloc的升级
#include <iostream>
#include <stdlib.h>
using namespace std;
class test
{
public:
test(int a)
{
cout<<"hello world"<<a<<endl;
}
test()
{
cout<<"hello world"<<endl;
}
~test()
{
cout<<"析构测试"<<endl;
}
};
int main()
{
//test *t=(test *)malloc(sizeof(test));
test *t=new test;//new test(100);
cout<<"+++++++++"<<endl;
delete t;
//free(p);
/*
test *t=new test[5];
delete[] t;
*/
}
- 使用堆空间的原因
- 直到运行时才知道需要多少空间
- 不知道对象的生存期到底有多长
- 直到运行时才知道一个对象需要多少内存空间
拷贝构造函数
#include <iostream>
using namespace std;
class test
{
int m_a;
public:
test (int a)
{
m_a=a;
cout<<"test construct"<<m_a<<endl;
}
~test()
{
cout<<"析构测试"<<endl;
}
/* test(const test &q)//test(test &q)
{
m_a=q.m_a;
}*///默认构造函数只能完成浅拷贝，将形参传给自身
void show()
{
cout<<"m_a="<<m_a<<endl;
}
};
void hello (test temp)
{
temp.show();
}//test temp(t1);
int main()
{
test t1(10);
t1.show();
//test t2(t1);
//t2.show();
hello(t1);
}
如果成员为指针类型，会造成系统浅拷贝
#include <iostream>
using namespace std;
class test
{
int *m_a;
public:
test(int a)
{
m_a=new int;
*m_a=a;
cout<<"test construct"<<*m_a<<endl;
}
~test()
{
cout<<"析构测试"<<endl;
delete m_a;
}
void show()
{
cout<<"m_a="<<*m_a<<endl;
}
test(const test &q)
{
m_a=new int;
*m_a=*q.m_a;
}//先分配空间再拷贝
};
int main()
{
test t1(10);
t1.show();
test t2(t1);
t2.show();
}//浅拷贝：创建t2时，t1被复制给了t
2，但是资源未被复制，因此t1，t2指向同一个资源。
- 为什么拷贝构造函数的传参都是引用
- 传值的方式会调用该类的拷贝构造函数，从而造成无穷递归地调用拷贝构 造函数。因此拷贝构造函数的参数必须是一个引用
- 仿写 string 类 ，取名 MyString
-
完成4种构造函数
- MyString s;
- MyString s("weiwei");
- MyString s1(5,'c');
- MyString s(s1);
- ~MyString() 要释放空间
if( NULL != m_str) { delete[]m_p;//指针释放完空间，必须指向NULL m_str = NULL; } 完成 size() / bool empty() 成员函数
String类中 只能有两个成员变量 char *m_str和int m_nLength
-
#include <iostream>
#include <string.h>
using namespace std;
class myString
{
char *m_str;
int m_length;
public:
myString();
myString(const char *ch);
myString(unsigned int length,const char &ch);
myString(const myString &s);
int size()
{
return m_length;
}
bool empty()
{
return m_length==0;
}
~myString()
{
if( NULL != m_str)
delete []m_str;
m_str=NULL;
}
void show()
{
cout<<m_str<<endl;
}
};
myString ::myString()
{
m_str=new char[1];
m_str=0;
m_length=0;
}
myString ::myString(const char *ch)
{
if(ch==NULL)
{
m_str=new char[1];
m_str=0;
m_length=0;
}
else
{
m_str=new char[sizeof(ch)+1];
strcpy(m_str,ch);
m_length=strlen(ch);
}
}
myString ::myString(unsigned int length,const char &ch)
{
int i;
m_length=length;
m_str=new char[length+1];
for(i=0;i<length;i++)
{
m_str[i]=ch;
}
m_str[length]='\0';
}
myString ::myString(const myString &s)
{
m_str=new char[sizeof(s.m_str)+1];
strcpy(m_str,s.m_str);
m_length=strlen(s.m_str);
}
int main()
{
myString s(5,'c');
myString s1(s);
s.show();
s1.show();
cout<<s.size()<<endl;
cout<<(s.empty()?"空":"不空")<<endl;
}
- josephus问题
#include <iostream>
#include<stdlib.h>
using namespace std;
typedef struct Node
{
int data;
struct Node *next;
}Node,*List;
class Ring//环链表
{
private:
List First;
int Count;
int Current;
//List Begin;
public:
void Print();
void Clear(){};
void Creatlist(int n,int m,int z);
void Pivot();
};
void Ring::Creatlist(int n,int m,int z)
{
List p;
int i;
First=(Node*)malloc(sizeof(Node));
if(!First)
{
cout<<"memory allocation error!\n";
return ;
}
First->data=1; First->next=First;
for(i=n;i>1;--i)
{
p=(Node*)malloc(sizeof(Node));
if(!p)
{
cout<<"memory allocation error!\n";
return;
}
p->data=i; p->next=First->next; First->next=p;
}
Count = n;
Current = m;
if(z<1)return;
for(int j = 0;j<z;j++)
{
First=First->next;
}bu
}
void Ring::Print()
{
List p=First;
do
{
cout<<p->data<<" ";
p=p->next;
}while(p!=First);
cout<<endl;
}
void Ring::Pivot()
{
Node* p=First,*pre=NULL;
int i,j;
for(i=0;i<Count-1;++i)
{
for(j=1;j<Current;++j)
{
pre=p;
p=p->next;
}
cout<<"出列的人是"<<p->data<<endl;
pre->next=p->next; free(p);
p=pre->next;
}
cout<<"The winner is "<<p->data<<endl;
}
class Josephus
{
private:
int Boynumber;//孩子数量
int Beginpos;//开始位置
int Inteval;//间隔
Ring Head;
public:
void Inital();//初始化
void Getwinner();//获得胜利者
void Output();
};
void Josephus::Inital()
{
cout<<"Input the Boynumber , Inteval and Beginpos:";
cin>>Boynumber>>Inteval>>Beginpos;
if(Inteval < 2)Inteval = 2;
Head.Creatlist(Boynumber,Inteval,Beginpos);
}
void Josephus::Getwinner()
{
Head.Pivot();
}
void Josephus::Output()
{
Head.Print();
}
int main()
{
Josephus jose;
jose.Inital();
jose.Output();
jose.Getwinner();
return 0;
}
