CPP_Basic_Code_P4.1-PP4.13.10

CPP_Basic_Code_P4.1-PP4.13.10

//  The Notes Created by Z-Tech on 2017/2/17.
//  All Codes Boot on 《C++ Primer Plus》V6.0
//  OS：MacOS 10.12.4
//  Translater：clang/llvm8.0.0 &g++4.2.1
//  Editer：iTerm 2&Sublime text 3
//  IDE: Xcode8.2.1&Clion2017.1

//P4.1
#include <iostream>
int main()
{
    using namespace std;
    int yams[3];
    yams[0]=7;
    yams[1]=8;
    yams[2]=6;

    int yamcosts[3]={20,30,5};
    cout<<"Total yams = ";
    cout<<yams[0]+yams[1]+yams[2]<<endl;
    cout<<"The package with "<<yams[1]<<"yams costs ";
    cout<<yamcosts[1]<<" cents per yam.\n";
    int total=yams[0]*yamcosts[0]+yams[1]*yamcosts[1];
    total=total+yams[2]*yamcosts[2];
    cout<<"The total yam expense is "<<total<<" cents.\n";

    cout<<"\nSize of yams array = "<<sizeof yams;//计算数组字节数
    cout<<" bytes.\n";
    cout<<"Size of one element = "<<sizeof yams[0];//计算数组单个成员字节数
    cout<<" bytes.\n";
    return 0;
}

//P4.2
#include <iostream>
int main()
{
    using namespace std;
    const int Size=15;
    char name1[Size];
    char name2[Size]="C++owboy";

    cout<<"Howdy! I'm "<<name2;
    cout<<"! What's yuour name?\n";
    cin>>name1;//这种方式的读取不允许姓名间有空格一类
    cout<<"Well, "<<name1<<", your name has ";
    cout<<strlen(name1)<<" letters and is stored\n";//提取字符串长度
    cout<<"in an array of "<<sizeof(name1)<<" bytes.\n";//数组所占字节数
    cout<<"Your initial is "<<name1[0]<<".\n";//第一个字母即第一个数组元素
    name2[3]='\0';//将数组name2的第四个元素置为"\0"
    cout<<"Here are the first 3 characters of my name: ";
    cout<<name2<<endl;//此时将读取前三个元素后即碰到\0，故只输出前三个
    return 0;
}

//P4.3
#include <iostream>
int main()
{
    using namespace std;
    const int Arsize=20;
    char name[Arsize];
    char dessert[Arsize];

    cout<<"Enter your name:\n";
    cin>>name;//由于此处不支持空格，会导致last name进入后面的cin队列，从而没有机会输入dessert
    cout<<"Enter your favorite dessert:\n";
    cin>>dessert;
    cout<<"I have some delicious "<<dessert;
    cout<<" for you, "<<name<<".\n";
    return 0;
}

//P4.4
#include <iostream>
int main()
{
    using namespace std;
    const int Arsize=20;//修改数组容量可以储存更多的字符串
    char name[Arsize];
    char dessert[Arsize];

    cout<<"Enter your name:\n";
    cin.getline(name,Arsize);//此处使用cin.getline面向行处理，成功克服空格问题
    cout<<"Enter your favorite dessert:\n";
    cin.getline(dessert,Arsize);//再次使用行处理
    cout<<"I have some delicious "<<dessert;
    cout<<" for you, "<<name<<".\n";
    return 0;
}

//P4.5
#include <iostream>
int main()
{
    using namespace std;
    const int Arsize=20;
    char name[Arsize];
    char dessert[Arsize];

    cout<<"Enter your name:\n";
    cin.get(name,Arsize).get();//这种方式会调用读取下一个字符（这里也就是回车）
    cout<<"Enter your favorite dessert:\n";
    cin.get(dessert,Arsize).get();//其实是cin.get(name,value)和cin.get()的合成缩写
    cout<<"I have some delicious "<<dessert;
    cout<<" for you, "<<name<<".\n";
    return 0;
}

//P4.6
#include <iostream>
int main()
{
    using namespace std;
    cout<<"What year was your house built?\n";
    int year;
    (cin>>year).get();//解决回车按键的问题
    cout<<"What's its street address?\n";
    char address[80];
    cin.getline(address,80);
    cout<<"Year built: "<<year<<endl;
    cout<<"Address: "<<address<<endl;
    cout<<"Done!\n";
    return 0;
}

//P4,7
#include <iostream>
#include <string>
int main()
{
    using namespace std;
    char charr1[20];
    char charr2[20]="jaguar";//数组式初始化
    string str1;
    string str2="panther";//C风格字符串的初始化

    cout<<"Enter a kind of feline: ";
    cin>>charr1;//可使用cin注入数组
    cout<<"Enter another kind of feline: ";
    cin>>str1;//可使用cin注入string对象
    cout<<"Here are some felines: \n";
    cout<<charr1<<" "<<charr2<<" "<<str1<<" "<<str2<<" "<<endl;
    cout<<"The third letter in "<<charr2<<" is "<< charr2[2]<<endl;//数组法引用
    cout<<"The third letter in "<<str2<<" is "<<str2[2]<<endl;//数组法引用string对象中的元素
    return 0;
}

//P4.8
#include <iostream>
#include <string>
int main()
{
    using namespace std;
    string s1="penguin";
    string s2,s3;
    cout<<"You can assign one string object to another:s2=s1\n";
    s2=s1;
    cout<<"s1: "<<s1<<" s2: "<<s2<<endl;
    cout<<"You can assign a C_Style string to a string object.\n";
    cout<<"s2=\"buzzard\"\n";
    s2="buzzard";//直接赋值
    cout<<"s2: "<<s2<<endl;
    cout<<"You can concatenate string:s3=s1+s2\n";
    s3=s1+s2;//直接合并两个字符串
    cout<<"s3:"<<s3<<endl;
    cout<<"You can append strings.\n";
    s1+=s2;//等价于s1=s1+s2，是添加运算符+=的效果
    cout<<"s1+=s2 yield s1 = "<<s1<<endl;
    s2+=" for a day!";//在结尾添加字符串
    cout<<"s2+= \" for a day!\" yield s2 = "<<s2<<endl;//使用string对象无需考虑字符串长度超出数组问题
    return 0;
}

//P4.9
#include <iostream>
#include <string>
#include <cstring>//C风格字符串
int main()
{
    using namespace std;
    char charr1[20];
    char charr2[20]="jaguar";
    string str1;
    string str2="panther";

    str1=str2;
    strcpy(charr1,charr2);//C风格字符串复制传递

    str1+=" paste";
    strcat(charr1," juice");//C风格字符串结尾添加字符

    int len1=str1.size();//子函数字符长度计算
    int len2=strlen(charr1);//C风格字符长度计算
    cout<<"The string "<<str1<<" contains "<<len1<<" characters.\n";
    cout<<"The string "<<charr1<<" contains "<<len2<<" charaters.\n";
    return 0;
}

//P4.10
#include <iostream>
#include <string>
#include <cstring>
int main()
{
    using namespace std;
    char charr[20];
    string str;

    cout<<"Length of string in charr before input: "
        <<strlen(charr)<<endl;//此时因未初始化，故字符内容不确定
    cout<<"Length of strinf in str before input: "
        <<str.size()<<endl;//因为是string对象，未初始化前内容自动为0
    cout<<"Enter a line of text:\n";
    cin.getline(charr,20);//经典C数组风格读取输入
    cout<<"You entered: "<<charr<<endl;
    cout<<"Enter another line of text: \n";
    getline(cin,str);//C++ string 对象读取，长度自适应
    cout<<"You entered: "<<str<<endl;
    cout<<"Length of string in charr after input: "
        <<strlen(charr)<<endl;
    cout<<"Length of string in str after input: "
        <<str.size()<<endl;
    return 0;
}

//P4.11
#include <iostream>
struct inflatable
{
    char name[20];
    float volume;
    double price;
};//注意结构体声明需要；结尾
int main()
{
    using namespace std;
    inflatable guest={"Glorious Gloria",1.88,29.99};//初始化结构成员guest
    inflatable pal={"Audacious Arthur",3.12,32.99};//初始化结构成员pal
    cout<<"Expand your guest list with "<<guest.name;
    cout<<" and "<<pal.name<<"!\n";//pal.name是一个char数组
    cout<<"You can have both for $";
    cout<<guest.price+pal.price<<"！\n";//guest.price是一个double变量
    return 0;
}

//P4.12
#include <iostream>
struct inflatable//结构化声明提倡使用外部式
{
    char name[20];
    float volume;
    double price;
};
int main()
{
    using namespace std;
    inflatable bouquet={"Sunflowers",0.20,12.49};
    inflatable choice;//未被初始化
    cout<<"bouquet: "<<bouquet.name<<" for $";
    cout<<bouquet.price<<endl;

    choice=bouquet;//结构体可以直接赋值，哪怕子结构中有数组
    cout<<"bouquet: "<<choice.name<<" for $";
    cout<<choice.price<<endl;
    return 0;
}

//P4.13
#include <iostream>
struct inflatable
{
    char name[20];
    float volume;
    double price;
};
int main()
{
    using namespace std;
    inflatable guest[2]=//此处[2]表明有两个结构
    {
       {"Bambi",0.5,21.99},
       {"Godzilla",2000,565.99}
    };//结构初始化之后必须加；

    cout<<"The guest "<<guest[0].name<<" and "<<guest[1].name
        <<"\nhave a combined volume of "
        <<guest[0].volume+guest[1].volume<<" cubic feet.\n";
    return 0;
}

//P4.14
#include <iostream>
int main()
{
    using namespace std;
    int donuts=6;
    double cups=4.5;
    cout<<"donuts value = "<<donuts;
    cout<<" and donuts address = "<<&donuts<<endl;//使用取址运算符&

    cout<<"cups avalue = "<<cups;
    cout<<" and cups address = "<<&cups<<endl;
    return 0;
}

//P4.15
#include <iostream>
int main()
{
    using namespace std;
    int updates=6;
    int* p_updates;//此处定义指针
    p_updates=&updates;//指针必须被赋值初始化

    cout<<"Value: updates = "<<updates;
    cout<<" , *p_updates = "<<*p_updates<<endl;//此处为所指向地址里的值

    cout<<"Address: &updates = "<<&updates;
    cout<<" , p_updates = "<<p_updates<<endl;//指针本身是一个地址

    ++*p_updates;//*p_updates可以像使用int变量一样操作
    cout<<"Now updates = "<<updates<<endl;
    return 0;
}

//P4.16
#include <iostream>
int main()
{
    using namespace std;
    int higgens=5;
    int* pt=&higgens;

    cout<<"Value of higgens = "<<higgens
        <<"; Address of higgens = "<<&higgens<<endl;
    cout<<"Value of *pt = "<<*pt//带*的指针即为对应的值
        <<"; Value of pt = "<<pt<<endl;//不带*即为指针本身，即地址
    return 0;
}

//P4.17
#include <iostream>
int main()
{
    using namespace std;
    int nights=1001;
    int* pt=new int;//申请了一块数据类型为int的新内存，且指针也指向int
    *pt=1001;

    cout<<"nights value = ";
    cout<<nights<<": location "<<&nights<<endl;//nights的地址
    cout<<"int ";
    cout<<"value = "<<*pt<<": location = "<<pt<<endl;
    double* pd=new double;//申请了一块数据类型为double的新内存且指向double
    *pd=10000001.0;

    cout<<"double ";
    cout<<"value = "<<*pd<<": location = "<<pd<<endl;//此处只能用pd来访问新申请的内存
    cout<<"location of pointer pd: "<<&pd<<endl;
    cout<<"size of pt = "<<sizeof(pt);//这里计算指针的字节数
    cout<<": size of *pt = "<<sizeof(*pt)<<endl;//这里是指针所指对象的值的字节数
    cout<<"size of pd = "<<sizeof(pd);//这里计算指针的字节数
    cout<<": size of *pd = "<<sizeof(*pd)<<endl;//这里是指针所指对象的值的字节数
    delete pt;
    delete pd;
    return 0;
}

//P4.18
#include <iostream>
int main()
{
    using namespace std;
    double* p3=new double[3];//new了一个3个元素的double数组
    p3[0]=0.2;
    p3[1]=0.5;
    p3[2]=0.8;
    cout<<"p3[1] is "<<p3[1]<<".\n";
    ++p3;//指针右移1个元素
    cout<<"Now p3[0] is "<<p3[0]<<" and ";
    cout<<"p3[1] is "<<p3[1]<<".\n";
    --p3;//指针移回原位，以备之后释放内存
    delete [] p3;//delete了之前new的内存
    return 0;
}

//P4.19
#include <iostream>
int main()
{
    using namespace std;
    double wages[3]={10000.0,20000.0,30000.0};
    short stacks[3]={3,2,1};

    double* pw=wages;//数组名为数组第一个元素的地址
    short* ps=&stacks[0];//这是上一句显式的写法

    cout<<"pw= "<<pw<<", *pw= "<<*pw<<endl;
    ++pw;//右移一个元素，double实际上是8字节
    cout<<"add 1 to the pw pointer:\n";
    cout<<"pw= "<<pw<<", *pw= "<<*pw<<"\n\n";
    cout<<"ps= "<<ps<<", *ps= "<<*ps<<endl;
    ++ps;//右移一个元素，short实际上是2字节
    cout<<"add 1 to ps pointer:\n";
    cout<<"ps= "<<ps<<", *ps= "<<*ps<<"\n\n";

    cout<<"access two elements with array notation\n";
    cout<<"stacks[0]= "<<stacks[0]<<",stacks[1]= "<<stacks[1]<<endl;
    //以上是直接访问数组元素的方式
    cout<<"access two elements with pointer notaion\n";
    cout<<"*stacks= "<<*stacks<<",*(stacks+1)= "<<*(stacks+1)<<endl;
    //以上是将数组名当做指针使用，移动提取元素的方式
    cout<<sizeof(wages)<<" = size of wages array\n";//计算整个数组的字节数
    cout<<sizeof(pw)<<" = size of pw pointer\n";//仅计算pw指针的字节数
    return 0;
}

//P4.20
#include <iostream>
#include <cstring>
int main()
{
    using namespace std;
    char animal[20]="bear";
    const char* bird="wren";//使用const可防止bird修改值wren
    char* ps;

    cout<<animal<<" and "<<bird<<endl;//cout对char类型默认为字符串输出
    cout<<"Enter a kind of animal: ";
    cin>>animal;
    ps=animal;
    cout<<ps<<"!\n";
    cout<<"before using strcpy():\n";
    cout<<animal<<" at "<<(int*)animal<<endl;//使用（int*)强制类型转换显示地址
    cout<<ps<<" at "<<(int*)ps<<endl;

    ps=new char[strlen(animal)+1];//申请新内存，且容量以animal为准再加1，以便存储空字符\0到结尾
    strcpy(ps,animal);
    cout<<"after using strcpy():\n";
    cout<<animal<<" at "<<(int*)animal<<endl;
    cout<<ps<<" at "<<(int*)ps<<endl;
    delete [] ps;
    return 0;
}

//P4.21
#include <iostream>
struct inflatable
{
    char name[20];
    float volume;
    double price;
};
int main()
{
    using namespace std;
    inflatable * ps=new inflatable;//新申请一个动态结构指针
    cout<<"Enter name of inflatable item: ";
    cin.get(ps->name,20);//指针法读取输入
    cout<<"Enter volume in cubic feet: ";
    cin>>(*ps).volume;//数组名引用法读取输入
    cout<<"Enter price: $";
    cin>>ps->price;
    cout<<"Name: "<<(*ps).name<<endl;
    cout<<"Volume: "<<ps->volume<<" cubic feet\n";
    cout<<"Price: $"<<ps->price<<endl;
    delete ps;//释放new出的内存
    return 0;
}

//P4.22
#include <iostream>
#include <cstring>
using namespace std;
char* getname(void);//函数声明，返回值为char，不接受参数
int main()
{
    char* name;
    name=getname();//第一次调用子函数
    cout<<name<<" at "<<(int*)name<<"\n";
    delete [] name;

    name=getname();//第二次调用子函数
    cout<<name<<" at "<<(int*)name<<"\n";
    delete [] name;//释放内存
    return 0;
}

char* getname()//子函数开始
{
    char temp[80];//建立临时字符串数组
    cout<<"Enter last name: ";
    cin>>temp;//读取字符串到数组temp
    char* pn=new char[strlen(temp)+1];//新定义恰到好处的指针和所需内存
    strcpy(pn,temp);//复制数据到新的指针地址

    return pn;//返回指针地址(char类型，将被识别为字符串本身)
}

//P4.23
#include <iostream>;

struct antarctica_years_end//结构定义
{
    int year;
};

int main()
{
    antarctica_years_end s01, s02, s03;//定义三个结构变量
    s01.year = 1998;//结构式赋值
    antarctica_years_end *pa = &s02;//定义结构指针pa指向s02
    pa->year = 1999;//指针式赋值
    antarctica_years_end trio[3];//创建三个元素的结构数组
    trio[0].year = 2003;//结构数组访问成员
    std::cout << trio->year << std::endl;
    //输出结构数组第一个元素结构的year成员 2003
    const antarctica_years_end *arp[3] = {&s01, &s02, &s03};//定义含3指针的指针数组
    //指针式访问第二个元素，即&s02指向结构变量的year成员1999
    const antarctica_years_end **ppa = arp;
    //创建指向上一个指针数组的的指针
    //或者使用const antarctica_years_end **ppb=arp
    std::cout<<(*ppa)->year<<std::endl;
    //ppa解除引用后，元素依然为指针(毕竟为指针数组第一个元素)1998
    //ppb和ppa一样，故+1后指针右移一个元素为&s02,1999
    return 0;
}

//P4.24
#include <iostream>
#include <vector>
#include <array>
int main()
{
    using namespace std;
    double a1[4]={1.2,2.4,3.6,4.8};//传统C语言写法初始化四元素数组

    vector<double> a2(4);//C++98方法初始化，动态数组替代品
    a2[0]=1.0/3.0;//初始化各个元素，C++98中没有捷径初始化
    a2[1]=1.0/5.0;
    a2[2]=1.0/7.0;
    a2[3]=1.0/9.0;

    array<double,4> a3={3.14,2.72,1.62,1.41};//静态内存分配，常规数组替代品
    array<double,4> a4;//被默认初始化为0
    a4=a3;

    cout<<"a1[2]: "<<a1[2]<<" at "<<&a1[2]<<endl;
    cout<<"a2[2]: "<<a2[2]<<" at "<<&a2[2]<<endl;
    cout<<"a3[2]: "<<a3[2]<<" at "<<&a3[2]<<endl;
    cout<<"a4[2]: "<<a4[2]<<" at "<<&a4[2]<<endl;

    a1[-2]=20.2;//即*(a1-2)，a1数组前移两个元素，已位于数组外部！可使用如：a2.at(1)=2.3
    cout<<"a1[-2]: "<<a1[-2]<<" at "<<&a1[-2]<<endl;
    cout<<"a3[2]: "<<a3[2]<<" at "<<&a3[2]<<endl;
    cout<<"a4[2]: "<<a4[2]<<" at "<<&a4[2]<<endl;
    return 0;
}

//PP4.13.1
#include <iostream>
//#include <cstring>
struct person
{
    char name1[20];
    char name2[20];
    char grade;//定义字符型变量
    int age;
};
int main()
{
    using namespace std;
    person* xv=new person;//new一个xv指向结构person
    cout<<"What is your first name? "<<endl;
    cin.getline(xv->name1,20);//使用getline以避免姓名中出现空格，造成\n被读取
    cout<<"What is your last name? "<<endl;
    cin.getline(xv->name2,20);
    cout<<"what letter grade do you deserve? "<<endl;
    cin>>(*xv).grade;//读入输入的成绩值
    cout<<"What is your age? "<<endl;
    cin>>xv->age;
    cout<<"Name: "<<xv->name2<<", "<<xv->name1<<endl;
    cout<<"Grade: "<<++(*xv).grade<<endl;//此处因为是字符型，只需++即可输出下一档次成绩值
    cout<<"Age: "<<xv->age<<endl;
    delete xv;//释放new出来的内存
    return 0;
}

//PP4.13.2
#include <iostream>
#include <string>
int main()
{
    using namespace std;

    string name;
    string dessert;

    cout<<"Enter your name:\n";
    getline(cin,name);//注意和数组的语法区别：cin.getline(name,30)
    cout<<"Enter your favorite dessert:\n";
    cin>>dessert;
    cout<<"I have some delicious "<<dessert;
    cout<<" for you, "<<name<<".\n";
    return 0;
}

//PP4.13.3
#include <iostream>
#include <cstring>
int main()
{
    using namespace std;
    char name1[20];
    char name2[20];
    cout<<"Enter your first name: "<<endl;
    cin.getline(name1,20);
    cout<<"Enter your last name: "<<endl;
    cin.getline(name2,20);
    strcat(name2,",");//C风格字符串的添加使用strcat()函数
    strcat(name2,name1);
    cout<<"Here's the information in single string: "<<endl
        <<name2;
    return 0;
}

//PP4.13.4
#include <iostream>
#include <string>
int main()
{
    using namespace std;
    string name1,name2,name;
    cout<<"Enter your first name: "<<endl;
    getline(cin,name1);//使用string对象的处理方式
    cout<<"Enter your last name: "<<endl;
    getline(cin,name2);
    name=name2+","+name1;//string类支持直接加合多个字符串且不用考虑长度问题
    cout<<"Here's the information in single string: "<<endl
        <<name;
    return 0;
}

//PP4.13.5
#include <iostream>
#include <string>
struct CandyBar
{
    std::string brand="Mocha Munch";
    float weight=2.3;
    int calorie=350;
}snack;//定义结构时即初始化变量snack
int main()
{
    std::cout<<"Brand: "<<snack.brand<<std::endl
             <<"Weight: "<<snack.weight<<std::endl
             <<"Calorie: "<<snack.calorie<<std::endl;
    return 0;
}

//PP4.13.6
#include <iostream>
#include <string>
struct CandyBar
{
    std::string brand;
    float weight;
    int calorie;
};
int main()
{
    CandyBar species[3];//初始化一个三元素的结构数组species
    species[0].brand="傻子";//数组法初始化
    species[0].weight=25.25;
    species[0].calorie=250;
    (species+1)->brand="聪明者";//数组名即为指针，故也可用指针法给第二个成员结构的元素赋值
    (species+1)->weight=36.66;
    (species+1)->calorie=360;
    CandyBar* xv[3]{&species[0],&species[1],&species[2]};
    //上一行开头处不用const可通过编译，新建指针数组，分别指向三个结构
    xv[2]->brand="普通人";//使用指针数组给第三个成员结构的元素赋值
    xv[2]->weight=22.33;
    xv[2]->calorie=290;
    std::cout<<"Brand1: "<<species[0].brand<<std::endl//输出第一个成员结构的品牌名
             <<"Weight2: "<<(species+1)->weight<<std::endl//输出第二个成员结构的产品重量
             <<"Calorie3: "<<xv[2]->calorie<<std::endl;//输出第三个成员结构的产品热量
    return 0;
}

//PP4.13.7&//PP4.13.8
#include <iostream>
#include <string>
using namespace std;
struct pizza
{
    string company_name;
    float pizza_diameter;
    float pizza_weight;
};
int main()
{
    pizza* xv=new pizza;
    cout<<"Enter the name of pizza company: "<<endl;
    getline(cin,xv->company_name);//注意语法细节，括号前面没有"."!!!
    cout<<"Enter the diameter of pizza: "<<endl;
    cin>>xv->pizza_diameter;
    cout<<"Enter the weight of pizza: "<<endl;
    cin>>xv->pizza_weight;
    cout<<"So here's the information you have input: "<<endl;
    cout<<"公司名称： "<<xv->company_name<<endl
        <<"披萨尺寸： "<<xv->pizza_diameter<<"寸"<<endl
        <<"披萨重量： "<<xv->pizza_weight<<"磅";
    delete xv;//注意释放New出的内存
    return 0;
}

//PP4.13.9
#include <iostream>
#include <string>
struct CandyBar
{
    std::string brand;
    float weight;
    int calorie;
};
int main()
{
    CandyBar* xv=new CandyBar;//一旦new了切记使用delete！
    xv->brand="傻瓜牌";
    xv->weight=250.55;
    xv->calorie=750;
    std::cout<<"品牌名： "<<xv->brand<<std::endl
             <<"重量： "<<xv->weight<<std::endl
             <<"热量： "<<xv->calorie<<std::endl;
    delete xv;
    return 0;
}

//PP4.13.10
#include <iostream>
#include <array>
int main()
{
    using namespace std;
    cout.setf(ios_base::fixed,ios_base::floatfield);//修复cout输出的小数点，防止整数时丢尾
    array<float,3> run_score;//注意array的初始化和声明方式，和数组区别
    enum run_times{zero,first,second,third};//试试枚举变量而已，另类的const
    cout<<"Enter your first score of 100meter: "<<endl;
    cin>>run_score[0];
    cout<<"Enter your second score of 100meter: "<<endl;
    cin>>run_score[1];
    cout<<"Enter your third score of 100meter: "<<endl;
    cin>>run_score[2];
    float mean_value=run_score[0]+run_score[1]+run_score[2];
    mean_value=(mean_value)/3;
    cout<<"Your NO."<<first<<" score of 100 meter: "<<run_score[0]<<"s"<<endl;
    cout<<"Your NO."<<second<<" score of 100 meter: "<<run_score[1]<<"s"<<endl;
    cout<<"Your NO."<<third<<" score of 100 meter: "<<run_score[2]<<"s"<<endl;
    cout<<"So your mean value score is: "<<mean_value<<"s"<<endl;
    return 0;
}