c++学习-数组

 

int a[10]; //是个元素，在windows下回报错，linux会输出一个随机数

int a[10]={1,2}; //初始化，其他的为0

 

数组越界：

为了调高效率， 编译器不会对数组越界做检查

#include <iostream>
using namespace std;


int main()
{
    
    int b[10];
    int a[2];
    b[10] = 3;

    cout<<b[10]<<endl;
    cout<<a[0]<<endl;

    return 0;
}

 

int a[10]; // 自动生成一个指针，该指针指向数组的第一个元素的地址  int *a=&a[0];

 数组的传递：

void test(int []);//简要数组声明
void test(int [10]);//标准数组声明
void test(int *a);//指针声明

 

数组对象：

#include<iostream>
using namespace std;

class area{
public:
    area(){}
    area(int w, int h){ this->w = w; this->h = h; cout << "gouzao" << endl; }
    ~area(){ cout << "xigou" << endl; }
    int get()
    {
        return w*h;
    }
private:
    int w;
    int h;
};


int main()
{
    area a[5] = {area(1,2),area(3,4)};

    cout << a[0].get() << endl;

    return 0;
    
}

 

指针数组：

#include<iostream>
using namespace std;

class area{
public:
    area(){ cout << "gouzao:" <<endl; }
    area(int i){ this->i = i; cout << "gouzao:" << i << endl; }
    area(int w, int h){ this->w = w; this->h = h; cout << "gouzao" << endl; }
    ~area(){ cout << "xigou "<<i << endl; }
    int get()
    {
        return w*h;
    }
private:
    int w;
    int h;
    int i;
};


int main()
{
    area *p[5];//指针数组
    int i;
    for (i = 0; i < 5; ++i)
    {
        p[i] = new area(i);
    }
    
    //释放内存
    for (i = 0; i < 5; ++i)
    {
        delete p[i];
    }
    
    return 0;
    
}

优化后：

#include<iostream>
using namespace std;

class area{
public:
    area(){ cout << "gouzao:" <<endl; }
    area(int i){ this->i = i; cout << "gouzao:" << i << endl; }
    area(int w, int h){ this->w = w; this->h = h; cout << "gouzao" << endl; }
    ~area(){ cout << "xigou "<<i << endl; }
    int get()
    {
        return w*h;
    }
    void set(int w, int h)
    {
        this->w = w;
        this->h = h;
    }
private:
    int w;
    int h;
    int i;
};


int main()
{

    area *p = new area[5]; //在堆中创建连续的五个对象，并将第一个对象的地址赋值给指针 p
    int i;
    
    for (i = 0; i < 5; i++)
    {
        p[i].set(i,i);
    }

    delete []p; //特有的删除方式

    return 0;
    
}

 

枚举常量和数组：

int main()
{
    
    enum day{mon, tue, wen, thur ,fri,sat, sun};
    double tempature[sun + 1] = { 5, 3, 4, 5, 5, 5, 6};

    int i;
    for (i = 0; i <= sun; i++)
    {
        cout << "xingqi " << i << "\t" << "qiwen:" << tempature[i] << endl;
    }
    
    
}

 

有 \0 直接输出数组名即可

int main()
{

    char c[] = {'a','b', '\0'};
    
    //cout << sizeof(c) << endl;
    cout << c << endl;
    
    return 0;

}

 

int main()
{

    char c[2];

    //cin >> c; //不检查是否越界，遇到空格会结束
    //gets(c); //不检查是否越界，会接收所有的字符
    cin.get(c,11);//解决上面问题

    cout << sizeof(c) << endl;
    //cout << (int)c[2] << endl;
    //cout << (int)c[0] << endl;
    
    return 0;

}

 strcat

int main()
{

    char a[10] = "ab";//注意第一个要足够的大
    char b[] = "cd";

    strcat(a, b); //连接时第一个字符串末尾的 '\0' 会自动去掉

    cout << a << endl;
    cout << sizeof(a) << endl;

    return 0;

}

 strcpy

int main()
{

    char a[10] = "ab";
    char b[] = "cd";

    strcpy(a,b); //b可以是一个字符串，注意a要足够大
    //strcpy(a, "def");

    cout << a << endl;
    cout << sizeof(a) << endl;

    return 0;

}

 

strcmp

int main()
{

    char a[10] = "ab";
    char b[] = "ab";

    if (strcmp(a, b) == 0) // strcmp("a", "b")
    {
        cout << "equal"<<endl;
    }
    
    return 0;

}

 

重载[]运算符解决数组越界问题：

class A{
public:
    A(int len){ this->len = len; p = new char[len]; }
    ~A(){ delete[]p; p = 0; }
    char & operator[](int i)
    {
        if (i<0 || i>=len)
        {
            cout << "越界" << endl;
            return *(p + len - 1);
        }
        else{
            return *(p + i);
        }
    }
private:
    int len;
    char *p;

};

int main()
{
    A a(5);

    int i;
    char *p = "abcdefghkjklmn";
    for (i = 0; i < 10; ++i)
    {
        a[i] = *(p + i);
    }

    for (int j = 0; j < 5; j++)
    {
        cout << a[j] << endl;
    }

    return 0;

}