C++ 复合类型（上）

//马铃薯分析程序
#include<iostream>
int main()
{
    using namespace std;
    int yams[3];//声明一个包含三个int类型元素的数组
    yams[0]=7;//数组下表从0开始
    yams[1]=8;
    yams[2]=6;

    int yamcosts[3]={20,30,5};//声明并初始化一个数组
    cout<<"Total yams=  "<<yams[0]+yams[1]+yams[2]<<endl;
    cout<<"The package with "<<yams[1]<<" yams costs "<<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<<"\n Size of yams array= "<<sizeof yams<<" bytes."<<endl;
    cout<<"Size of one element= "<<sizeof yams[0]<<" bytes."<<endl;
    return 0;
}

/将一个数组初始化为用引号括起来的字符串，使用cin将一个输入字符串放到另一个数组中
//使用strlen()确定字符串的长度
#include<iostream>
#include<cstring>//提供strlen()函数原型
int main()
{
    using namespace std;
    const int Size=15;//使用关键字
    char name1[Size];
    char name2[Size]="C++owboy";

    cout<<"Howdy! I‘m "<<name2<<" ! What‘s your name?"<<endl;
    cin>>name1;
    cout<<"Well, "<<name1<<" , your name has "<<strlen(name1)<<" letters and is stored\n";
    cout<<"in an array of "<<sizeof (name1)<<" bytes."<<endl;          
    cout<<"You initial ia "<<name1[0]<<".\n";
    name2[3]=‘\0‘;
    cout<<"Here are the first 3 characters of my name: "<<name2<<endl;
    return 0;
}
//sizeof操作符指出整个数组的长度，strlen()函数返回的是存储在数组中的字符串的长度，而不是数组本身的长度
//strlen()只计算可见的字符，不把空字符计算在内。

//面向行输入  getline()函数
#include<iostream>
int main()
{
    using namespace std;
    const int AriSize=20;
    char name[AriSize];
    char dessert[AriSize];

    cout<<"Enter your name:\n";
    cin.getline(name,AriSize);
    cout<<"Enter your favorite dessert:\n";
    cin.getline(dessert,AriSize);
    cout<<"I have some delicious "<<dessert<<" for you,"<<name<<".\n";
    return 0;
}

 1 //使用get()函数将两个类成员函数拼接
 2 //把输入中连续的两行分别读入到数组name1和数组name2中
 3 #include<iostream>
 4 int main()
 5 {
 6     using namespace std;
 7     const int AriSize=20;
 8     char name[AriSize];
 9     char dessert[AriSize];
10 
11     cout<<"Enter your name:\n";
12     cin.getline(name,AriSize).get();
13     cout<<"Enter your favorite dessert:\n";
14     cin.getline(dessert,AriSize).get();
15     cout<<"I have some delicious "<<dessert<<" for you,"<<name<<".\n";
16     return 0;
17 }

 1 //混合输入字符串和数字
 2 /*
 3 #include<iostream>
 4 int main()
 5 {
 6     using namespace std;
 7     cout<<"What‘s year was your house bulit?\n";
 8     int year;
 9     cin>>year;
10     cout<<"What‘s is its street address?\n";
11     char address[80];
12     cin.getline(address,80);
13     cout<<"Year bulit: "<<year<<endl;
14     cout<<"Address: "<<address<<endl;
15     cout<<"Done!"<<endl;
16     return 0;
17 }
18 */
19 #include<iostream>
20 int main()
21 {
22     using namespace std;
23     cout<<"What‘s year was your house bulit?\n";
24     int year;
25     (cin>>year).get();//两种方式，在读取地址之前，先读取并丢弃换行符。
26     //cin.get();
27     cout<<"What‘s is its street address?\n";
28     char address[80];
29     cin.getline(address,80);
30     cout<<"Year bulit: "<<year<<endl;
31     cout<<"Address: "<<address<<endl;
32     cout<<"Done!"<<endl;
33     return 0;
34 }

 1 //string对象与字符数组之间的一些相同点和不同点
 2 //string对象和字符数组的主要区别是可以讲string对象声明为简单变量而不是数组
 3 //类设计让程序能够自动处理string的大小。
 4 #include<iostream>
 5 #include<string>
 6 int main()
 7 {
 8     using namespace std;
 9     char char1[20];
10     char char2[20]="yang";
11     string str1;
12     string str2="yong";
13 
14     cout<<"Enter a kind of feline: ";
15     cin>>char1;
16     cout<<"Enter another kind of feline: ";
17     cin>>str1;
18     cout<<"Here are some felines:\n";
19     cout<<char1<<" "<<char2<<" "<<str1<<" "<<str2<<endl;
20     cout<<"The third letter in "<<char2<<" is"<<char2[2]<<endl;
21     cout<<"The third letter in "<<str2<<" is"<<str2[2]<<endl;
22     return 0;
23 }

 1  //字符串的赋值、拼接和附加
 2 #include<iostream>
 3 #include<string>
 4 int main()
 5 {
 6     using namespace std;
 7     string s1="heyun";
 8     string s2,s3;
 9     cout<<"You can assigan one string object to another:s2=s1: \n";
10     s2=s1;
11     cout<<"s1= "<<s1<<"s2= "<<s2<<endl;
12     cout<<"You can assigan a C—style string to a string object.\n";
13     cout<<"s2= \"buzzard\"\n";//打印双引号,初始化s2
14     s2="buzzard";
15     cout<<"s2= "<<s2<<endl;
16     cout<<"You can concatenate strings:s3=s1+s2\n";
17     s3=s1+s2;
18     cout<<"s3= "<<s3<<endl;
19     cout<<"You can append strings.\n";
20     s1+="for a day";
21     cout<<"s1+=s2 yields s1= "<<s1<<endl;
22     s2+="for a day";
23     cout<<"s2+=\"for a day\" yields s2= "<<s2<<endl;
24 
25     return 0;
26 }

 1 //对用于string对象的技术和用于字符数组的技术进行了比较
 2 #include<iostream>
 3 #include<string>
 4 #include<cstring>//函数原型
 5 int  main()
 6 {
 7     using namespace std;
 8     char char1[20];
 9     char char2[20]="jaguar";//初始化数组
10     string str1;
11     string str2="panther";
12 
13     str1=str2;//赋值
14     strcpy(char1,char2);//将字符串复制
15 
16     str1+="paste";//附加
17     strcat(char1,"juice");//将字符串附加
18 
19     int len1=str1.size();//计算str1的长度，用size()
20     int len2=strlen(char1);//计算char1的长度，用strlen函数
21     
22     cout<<"The string  "<<str1<<" contains "<<len1<<" characters.\n";
23     cout<<"The string "<<char1<<" contains "<<len2<<" characters.\n";
24 
25     return 0;
26 }

 1 #include<iostream>
 2 #include<string>
 3 #include<cstring>
 4 int main()
 5 {
 6     using namespace std;
 7     char charr[20];
 8     string str;
 9 //strlen()
10     cout<<"Length of string in charr before input: "<<strlen(charr)<<endl;
11     cout<<"Length of string in str before input: "<<str.size()<<endl;//未被初始化的string对象的长度自动设置为0
12     cout<<"Enter a line of text:\n";
13     cin.getline(charr,20);//(目标数组，数组长度），istream类的一个类方法
14     cout<<"You entered: "<<charr<<endl;
15     cout<<"Enter another line of text:\n";
16     getline(cin,str);//这个getline()不是类方法
17     cout<<"You entered: "<<str<<endl;
18     cout<<"Length of string in charr after input: "<<strlen(charr)<<endl;
19     cout<<"Length of string in str after input: "<<str.size()<<endl;
20     return 0;
21 }