C++ primer plus(第六版)编程练习答案第4章复合类型

古城微笑少年丶 2024-03-24 08:33 92阅读 0赞

## 一、程序清单 ##

## arrayone.cpp ##

// arrayone.cpp -- small arrays of integers
    #include <iostream>
    int main()
    {
    	using namespace std;
    	int yams[3];    // creates array with three elements
    	yams[0] = 7;    // assign value to first element
    	yams[1] = 8;
    	yams[2] = 6;
    
    	int yamcosts[3] = { 20, 30, 5 }; // create, initialize array
    // NOTE: If your C++ compiler or translator can't initialize
    // this array, use static int yamcosts[3] instead of
    // int yamcosts[3]
    
    	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;
    	cout << " bytes.\n";
    	cout << "Size of one element = " << sizeof yams[0];
    	cout << " bytes.\n";
    	// cin.get();
    	return 0;
    }

执行结果：

Total yams = 21
    The package with 8 yams costs 30 cents per yam.
    The total yam expense is 410 cents.
    
    Size of yams array = 12 bytes.
    Size of one element = 4 bytes.

## strings.cpp ##

// strings.cpp -- storing strings in an array
    #include <iostream>
    #include <cstring>  // for the strlen() function
    int main()
    {
        using namespace std;
        const int Size = 15;
        char name1[Size];               // empty array
        char name2[Size] = "C++owboy";  // initialized array
        // NOTE: some implementations may require the static keyword
        // to initialize the array name2
    
        cout << "Howdy! I'm " << name2;
        cout << "! What's your name?\n";
        cin >> name1;
        cout << "Well, " << name1 << ", your name has ";
        cout << strlen(name1) << " letters and is stored\n";
        cout << "in an array of " << sizeof(name1) << " bytes.\n";
        cout << "Your initial is " << name1[0] << ".\n";
        name2[3] = '\0';                // set to null character
        cout << "Here are the first 3 characters of my name: ";
        cout << name2 << endl;
        // cin.get();
        // cin.get();
        return 0;
    }

执行结果：

Howdy! I'm C++owboy! What's your name?
    Basicman
    Well, Basicman, your name has 8 letters and is stored
    in an array of 15 bytes.
    Your initial is B.
    Here are the first 3 characters of my name: C++

## instr1.cpp ##

// instr1.cpp -- reading more than one string
    #include <iostream>
    int main()
    {
    	using namespace std;
    	const int ArSize = 20;
    	char name[ArSize];
    	char dessert[ArSize];
    
    	cout << "Enter your name:\n";
    	cin >> name;
    	cout << "Enter your favorite dessert:\n";
    	cin >> dessert;
    	cout << "I have some delicious " << dessert;
    	cout << " for you, " << name << ".\n";
    	// cin.get();
    	// cin.get();
    	return 0;
    }

执行结果：

Enter your name:
    Alistair Dreab
    Enter your favorite dessert:
    I have some delicious Dreab for you, Alistair.

instr2.cpp

// instr2.cpp -- reading more than one word with getline
    #include <iostream>
    int main()
    {
        using namespace std;
        const int ArSize = 20;
        char name[ArSize];
        char dessert[ArSize];
    
        cout << "Enter your name:\n";
        cin.getline(name, ArSize);  // reads through newline
        cout << "Enter your favorite dessert:\n";
        cin.getline(dessert, ArSize);
        cout << "I have some delicious " << dessert;
        cout << " for you, " << name << ".\n";
        // cin.get();
        return 0; 
    }

执行结果：

Enter your name:
    Dirk Hammernose
    Enter your favorite dessert:
    Radish Torte
    I have some delicious Radish Torte for you, Dirk Hammernose.

## instr3.cpp ##

// instr3.cpp -- reading more than one word with get() & get()
    #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();    // read string, newline
    	cout << "Enter your favorite dessert:\n";
    	cin.get(dessert, ArSize).get();
    	cout << "I have some delicious " << dessert;
    	cout << " for you, " << name << ".\n";
    	// cin.get();
    	return 0;
    }

执行结果：

Enter your name:
    Mai Parfait
    Enter your favorite dessert:
    Chocolate Mousse
    I have some delicious Chocolate Mousse for you, Mai Parfait.

## numstr.cpp ##

// numstr.cpp -- following number input with line input
    #include <iostream>
    int main()
    {
        using namespace std;
        cout << "What year was your house built?\n";
        int year;
        cin >> year;
        // cin.get();
        cout << "What is its street address?\n";
        char address[80];
        cin.getline(address, 80);
        cout << "Year built: " << year << endl;
        cout << "Address: " << address << endl;
        cout << "Done!\n";
        // cin.get();
        return 0; 
    }

执行结果：

What year was your house built?
    1966
    What is its street address?
    Year built: 1966
    Address:
    Done!

## strtype1.cpp ##

// strtype1.cpp -- using the C++ string class
    #include <iostream>
    #include <string>               // make string class available
    int main()
    {
    	using namespace std;
    	char charr1[20];            // create an empty array
    	char charr2[20] = "jaguar"; // create an initialized array
    	string str1;                // create an empty string object
    	string str2 = "panther";    // create an initialized string
    
    	cout << "Enter a kind of feline: ";
    	cin >> charr1;
    	cout << "Enter another kind of feline: ";
    	cin >> str1;                // use cin for input
    	cout << "Here are some felines:\n";
    	cout << charr1 << " " << charr2 << " "
    		<< str1 << " " << str2 // use cout for output
    		<< endl;
    	cout << "The third letter in " << charr2 << " is "
    		<< charr2[2] << endl;
    	cout << "The third letter in " << str2 << " is "
    		<< str2[2] << endl;    // use array notation
       // cin.get();
       // cin.get();
    
    	return 0;
    }

执行结果：

Enter a kind of feline: ocelot
    Enter another kind of feline: tiger
    Here are some felines:
    ocelot jaguar tiger panther
    The third letter in jaguar is g
    The third letter in panther is n

## strtype2.cpp ##

// strtype2.cpp -- assigning, adding, and appending
    #include <iostream>
    #include <string>               // make string class available
    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";
    	cout << "s2: " << s2 << endl;
    	cout << "You can concatenate strings: s3 = s1 + s2\n";
    	s3 = s1 + s2;
    	cout << "s3: " << s3 << endl;
    	cout << "You can append strings.\n";
    	s1 += s2;
    	cout << "s1 += s2 yields s1 = " << s1 << endl;
    	s2 += " for a day";
    	cout << "s2 += \" for a day\" yields s2 = " << s2 << endl;
    
    	//cin.get();
    	return 0;
    }

执行结果：

You can assign one string object to another: s2 = s1
    s1: penguin, s2: penguin
    You can assign a C-style string to a string object.
    s2 = "buzzard"
    s2: buzzard
    You can concatenate strings: s3 = s1 + s2
    s3: penguinbuzzard
    You can append strings.
    s1 += s2 yields s1 = penguinbuzzard
    s2 += " for a day" yields s2 = buzzard for a day

## strtype3.cpp ##

// strtype3.cpp -- more string class features
    #include <iostream>
    #include <string>               // make string class available
    #include <cstring>              // C-style string library
    #pragma warning(disable:4996)
    int main()
    {
    	using namespace std;
    	char charr1[20];
    	char charr2[20] = "jaguar";
    	string str1;
    	string str2 = "panther";
    
    	// assignment for string objects and character arrays
    	str1 = str2;                // copy str2 to str1
    	strcpy(charr1, charr2);     // copy charr2 to charr1
    
    	// appending for string objects and character arrays
    	str1 += " paste";           // add paste to end of str1
    	strcat(charr1, " juice");   // add juice to end of charr1
    
    	// finding the length of a string object and a C-style string
    	int len1 = str1.size();     // obtain length of str1
    	int len2 = strlen(charr1);  // obtain length of charr1
    
    	cout << "The string " << str1 << " contains "
    		<< len1 << " characters.\n";
    	cout << "The string " << charr1 << " contains "
    		<< len2 << " characters.\n";
    	// cin.get();
    
    	return 0;
    }

执行结果：

The string panther paste contains 13 characters.
    The string jaguar juice contains 12 characters.

## ERROR解决： ##

> 'strcpy': This function or variable may be [unsafe][]. Consider using strcpy\_s instead. To disable deprecation, use \_CRT\_SECURE\_NO\_WARNINGS. See online help for details.

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## strtype4.cpp ##

// strtype4.cpp -- line input
    #include <iostream>
    #include <string>               // make string class available
    #include <cstring>              // C-style string library
    int main()
    {
        using namespace std;
        char charr[20]; 
        string str;
    
        cout << "Length of string in charr before input: " 
             << strlen(charr) << endl;
        cout << "Length of string in str before input: "
             << str.size() << endl;
        cout << "Enter a line of text:\n";
        cin.getline(charr, 20);     // indicate maximum length
        cout << "You entered: " << charr << endl;
        cout << "Enter another line of text:\n";
        getline(cin, str);          // cin now an argument; no length specifier
        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;
        // cin.get();
    
        return 0; 
    }

执行结果：

Length of string in charr before input: 31
    Length of string in str before input: 0
    Enter a line of text:
    peanut butter
    You entered: peanut butter
    Enter another line of text:
    blueberry jam
    You entered: blueberry jam
    Length of string in charr after input: 13
    Length of string in str after input: 13

## structur.cpp ##

// structur.cpp -- a simple structure
    #include <iostream>
    struct inflatable   // structure declaration
    {
        char name[20];
        float volume;
        double price;
    };
    
    int main()
    {
        using namespace std;
        inflatable guest =
        {
            "Glorious Gloria",  // name value
            1.88,               // volume value
            29.99               // price value
        };  // guest is a structure variable of type inflatable
    // It's initialized to the indicated values
        inflatable pal =
        {
            "Audacious Arthur",
            3.12,
            32.99
        };  // pal is a second variable of type inflatable
    // NOTE: some implementations require using
    // static inflatable guest =
    
        cout << "Expand your guest list with " << guest.name;
        cout << " and " << pal.name << "!\n";
    // pal.name is the name member of the pal variable
        cout << "You can have both for $";
        cout << guest.price + pal.price << "!\n";
        // cin.get();
        return 0; 
    }

执行结果：

Expand your guest list with Glorious Gloria and Audacious Arthur!
    You can have both for $62.98!

## assgn\_st.cpp ##

// assgn_st.cpp -- assigning structures
    #include <iostream>
    struct inflatable
    {
    	char name[20];
    	float volume;
    	double price;
    };
    int main()
    {
    	using namespace std;
    	inflatable bouquet =
    	{
    		"sunflowers",
    		0.20,
    		12.49
    	};
    	inflatable choice;
    	cout << "bouquet: " << bouquet.name << " for $";
    	cout << bouquet.price << endl;
    
    	choice = bouquet;  // assign one structure to another
    	cout << "choice: " << choice.name << " for $";
    	cout << choice.price << endl;
    	// cin.get();
    	return 0;
    }

执行结果：

bouquet: sunflowers for $12.49
    choice: sunflowers for $12.49

## **arrstruc.cpp**  ##

// arrstruc.cpp -- an array of structures
    #include <iostream>
    struct inflatable
    {
    	char name[20];
    	float volume;
    	double price;
    };
    int main()
    {
    	using namespace std;
    	inflatable guests[2] =          // initializing an array of structs
    	{
    		{"Bambi", 0.5, 21.99},      // first structure in array
    		{"Godzilla", 2000, 565.99}  // next structure in array
    	};
    
    	cout << "The guests " << guests[0].name << " and " << guests[1].name
    		<< "\nhave a combined volume of "
    		<< guests[0].volume + guests[1].volume << " cubic feet.\n";
    	// cin.get();
    	return 0;
    }

执行结果：

The guests Bambi and Godzilla
    have a combined volume of 2000.5 cubic feet.

## address.cpp ##

// address.cpp -- using the & operator to find addresses
    #include <iostream>
    int main()
    {
        using namespace std;
        int donuts = 6;
        double cups = 4.5;
    
        cout << "donuts value = " << donuts;
        cout << " and donuts address = " << &donuts << endl;
    // NOTE: you may need to use unsigned (&donuts)
    // and unsigned (&cups)
        cout << "cups value = " << cups;
        cout << " and cups address = " << &cups << endl;
        // cin.get();
        return 0; 
    }

执行结果：

donuts value = 6 and donuts address = 010FFD90
    cups value = 4.5 and cups address = 010FFD80

## pointer.cpp ##

// pointer.cpp -- our first pointer variable
    #include <iostream>
    int main()
    {
        using namespace std;
        int updates = 6;        // declare a variable
        int * p_updates;        // declare pointer to an int
    
        p_updates = &updates;   // assign address of int to pointer
    
    // express values two ways
        cout << "Values: updates = " << updates;
        cout << ", *p_updates = " << *p_updates << endl;
    
    // express address two ways
        cout << "Addresses: &updates = " << &updates;
        cout << ", p_updates = " << p_updates << endl;
    
    // use pointer to change value
        *p_updates = *p_updates + 1;
        cout << "Now updates = " << updates << endl;
        // cin.get();
        return 0; 
    }

执行结果：

Values: updates = 6, *p_updates = 6
    Addresses: &updates = 010FFE2C, p_updates = 010FFE2C
    Now updates = 7

## init\_ptr.cpp ##

// init_ptr.cpp -- initialize a pointer
    #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
             << "; Value of pt = " << pt << endl;
        // cin.get();
        return 0; 
    }

执行结果：

Value of higgens = 5; Address of higgens = 004FFC38
    Value of *pt = 5; Value of pt = 004FFC38

## use\_new.cpp ##

// use_new.cpp -- using the new operator
    #include <iostream>
    int main()
    {
    	using namespace std;
    	int nights = 1001;
    	int * pt = new int;         // allocate space for an int
    	*pt = 1001;                 // store a value there
    
    	cout << "nights value = ";
    	cout << nights << ": location " << &nights << endl;
    	cout << "int ";
    	cout << "value = " << *pt << ": location = " << pt << endl;
    
    	double * pd = new double;   // allocate space for a double
    	*pd = 10000001.0;           // store a double there
    
    	cout << "double ";
    	cout << "value = " << *pd << ": location = " << pd << endl;
    	cout << "location of pointer pd: " << &pd << endl;
    	cout << "size of pt = " << sizeof(pt);
    	cout << ": size of *pt = " << sizeof(*pt) << endl;
    	cout << "size of pd = " << sizeof pd;
    	cout << ": size of *pd = " << sizeof(*pd) << endl;
    	// cin.get();
    	return 0;
    }

执行结果：

nights value = 1001: location 010FFA38
    int value = 1001: location = 0138CEC8
    double value = 1e+07: location = 01386038
    location of pointer pd: 010FFA20
    size of pt = 4: size of *pt = 4
    size of pd = 4: size of *pd = 8

## arraynew.cpp ##

// arraynew.cpp -- using the new operator for arrays
    #include <iostream>
    int main()
    {
        using namespace std;
        double * p3 = new double [3]; // space for 3 doubles
        p3[0] = 0.2;                  // treat p3 like an array name
        p3[1] = 0.5;
        p3[2] = 0.8;
        cout << "p3[1] is " << p3[1] << ".\n";
        p3 = p3 + 1;                  // increment the pointer
        cout << "Now p3[0] is " << p3[0] << " and ";
        cout << "p3[1] is " << p3[1] << ".\n";
        p3 = p3 - 1;                  // point back to beginning
        delete [] p3;                 // free the memory
        // cin.get();
        return 0; 
    }

执行结果：

p3[1] is 0.5.
    Now p3[0] is 0.5 and p3[1] is 0.8.

## addpntrs.cpp ##

// addpntrs.cpp -- pointer addition
    #include <iostream>
    int main()
    {
    	using namespace std;
    	double wages[3] = { 10000.0, 20000.0, 30000.0 };
    	short stacks[3] = { 3, 2, 1 };
    
    	// Here are two ways to get the address of an array
    	double * pw = wages;     // name of an array = address
    	short * ps = &stacks[0]; // or use address operator
    // with array element
    	cout << "pw = " << pw << ", *pw = " << *pw << endl;
    	pw = pw + 1;
    	cout << "add 1 to the pw pointer:\n";
    	cout << "pw = " << pw << ", *pw = " << *pw << "\n\n";
    
    	cout << "ps = " << ps << ", *ps = " << *ps << endl;
    	ps = ps + 1;
    	cout << "add 1 to the 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;
    	cout << "access two elements with pointer notation\n";
    	cout << "*stacks = " << *stacks
    		<< ", *(stacks + 1) =  " << *(stacks + 1) << endl;
    
    	cout << sizeof(wages) << " = size of wages array\n";
    	cout << sizeof(pw) << " = size of pw pointer\n";
    	// cin.get();
    	return 0;
    }

执行结果：

pw = 0070FDE4, *pw = 10000
    add 1 to the pw pointer:
    pw = 0070FDEC, *pw = 20000
    
    ps = 0070FDD4, *ps = 3
    add 1 to the ps pointer:
    ps = 0070FDD6, *ps = 2
    
    access two elements with array notation
    stacks[0] = 3, stacks[1] = 2
    access two elements with pointer notation
    *stacks = 3, *(stacks + 1) =  2
    24 = size of wages array
    4 = size of pw pointer

## ptrstr.cpp ##

// ptrstr.cpp -- using pointers to strings
    #include <iostream>
    #include <cstring>              // declare strlen(), strcpy()
    #pragma warning(disable:4996)
    int main()
    {
        using namespace std;
        char animal[20] = "bear";   // animal holds bear
        const char * bird = "wren"; // bird holds address of string
        char * ps;                  // uninitialized
    
        cout << animal << " and ";  // display bear
        cout << bird << "\n";       // display wren
        // cout << ps << "\n";      //may display garbage, may cause a crash
    
        cout << "Enter a kind of animal: ";
        cin >> animal;              // ok if input < 20 chars
        // cin >> ps; Too horrible a blunder to try; ps doesn't
        //            point to allocated space
    
        ps = animal;                // set ps to point to string
        cout << ps << "!\n";       // ok, same as using animal
        cout << "Before using strcpy():\n";
        cout << animal << " at " << (int *) animal << endl;
        cout << ps << " at " << (int *) ps << endl;
    
        ps = new char[strlen(animal) + 1];  // get new storage
        strcpy(ps, animal);         // copy string to new storage
        cout << "After using strcpy():\n";
        cout << animal << " at " << (int *) animal << endl;
        cout << ps << " at " << (int *) ps << endl;
        delete [] ps;
        // cin.get();
        // cin.get();
        return 0; 
    }

执行结果：

bear and wren
    Enter a kind of animal: fox
    fox!
    Before using strcpy():
    fox at 010FF91C
    fox at 010FF91C
    After using strcpy():
    fox at 010FF91C
    fox at 01339380

## newstrct.cpp ##

// newstrct.cpp -- using new with a structure
    #include <iostream>
    struct inflatable   // structure definition
    {
        char name[20];
        float volume;
        double price;
    };
    int main()
    {
        using namespace std;
        inflatable * ps = new inflatable; // allot memory for structure
        cout << "Enter name of inflatable item: ";
        cin.get(ps->name, 20);            // method 1 for member access
        cout << "Enter volume in cubic feet: ";
        cin >> (*ps).volume;              // method 2 for member access
        cout << "Enter price: $";
        cin >> ps->price;
        cout << "Name: " << (*ps).name << endl;              // method 2
        cout << "Volume: " << ps->volume << " cubic feet\n"; // method 1
        cout << "Price: $" << ps->price << endl;             // method 1
        delete ps;                        // free memory used by structure
        // cin.get();
        // cin.get();
        return 0; 
    }

执行结果：

Enter name of inflatable item: Febulous Frodo
    Enter volume in cubic feet:
    7
    Enter price: $27.99
    Name: Febulous Frodo
    Volume: 7 cubic feet
    Price: $27.99

## delete.cpp ##

// delete.cpp -- using the delete operator
    #include <iostream>
    #include <cstring>      // or string.h
    using namespace std;
    char * getname(void);   // function prototype
    int main()
    {
    	char * name;        // create pointer but no storage
    
    	name = getname();   // assign address of string to name
    	cout << name << " at " << (int *)name << "\n";
    	delete[] name;     // memory freed
    
    	name = getname();   // reuse freed memory
    	cout << name << " at " << (int *)name << "\n";
    	delete[] name;     // memory freed again
    	// cin.get();
    	// cin.get();
    	return 0;
    }
    
    char * getname()        // return pointer to new string
    {
    	char temp[80];      // temporary storage
    	cout << "Enter last name: ";
    	cin >> temp;
    	char * pn = new char[strlen(temp) + 1];
    	strcpy(pn, temp);   // copy string into smaller space
    
    	return pn;          // temp lost when function ends
    }

执行结果：

Enter name of inflatable item: Febulous Frodo
    Enter volume in cubic feet:
    7
    Enter price: $27.99
    Name: Febulous Frodo
    Volume: 7 cubic feet
    Price: $27.99

## 二、复习题 ##

1.如何声明下述数据？

`a. actor是由30个char组成的数组`  
`b. betsie是由100个short组成的数组`  
`c. chuck是由13个float组成的数组`  
`d. dipsea是由64个long double组成的数组`

char actor[30];
    short betsie[100];
    float chuck[13];
    long double dipsea[64];

2.使用模板类数组而不是数组来完成1的问题。

array<char,30>actor;
    array<short,100>betsie;
    arry<float,13>chuck;
    array<long double,64>dipsea;

3.声明一个包含5个元素的int数组，并将他们初始化为前5个正奇数。

int a[5]={1,3,5,7,9};

4.编写一条语句，将问题3中数组第一个元素和最后一个元素的和赋值给变量even。

int a[5]={1,3,5,7,9};
    int even=a[0]+a[4];

5.编写一条语句，显示float数组ideas中的第二个元素的值。

cout<<ideas[1]<<endl;

6.声明一个char的数组，并将其初始化为字符串“Cheeseburger”。

char a[]="cheeseburger";

7.声明一个字符串对象，并将其初始化为字符串“Waldorf Salad”。

string a="Waldorf Salad";

8.设计一个描述鱼的结构声明，结构中应当包括品种、重量（整数，单位为盎司）和长度（英寸，包括小数）。

struct fish{
        char kind[20];
        int weight;
        float length;
    }

9.声明8中定义的结构变量，并对她进行初始化。

fish Xfish=
    {
        "xiaoyu";
        10;
        20.5;
    }

10.用enum定义一个名为Response的类型，它包含Yes、No和Maybe等枚举量，其中Yes的值为1，No为0，Maybe为2.

enum Response{No,Yes,Maybe};

11.假设ted是一个double变量，请声明一个指向ted的指针，并使用该指针来显示ted的值。

double *p=&ted;
    cout<<*p<<endl;

12.假设treacle是一个包含10个元素的float数组，请声明一个指向treacle的第一个元素的指针，并使用该指针来显示数组的第一元素和最后一个元素。

float *p=treacle;
    cout<<p[0]<<" "<<p[9]<<endl;
    //or cout<<*p<<"  "<<*(p+10) ;

13.编写一段代码，要求用户输入一个正整数，然后创建一个动态int数组，其中包含的元素数目等于用户的输入值，首先使用new来完成这项任务，再使用vector对象完成这项任务。

//use new
    int num;
    cout<<"Please input a positive integer: ";
    cin>>num;
    int *shu=new int[num];
    
    //use vector
    int num;
    cout<<"Please input a number: ";
    cin>>num;
    vector<int>shu(num);

14.下面的代码是否有效，如果有效，他将输出什么结果。

`cout<<(int*)"Home of the jolly bytes";`  
有效，输出该字符串的地址。

15.编写一段代码，给问题8中的结构动态分配内存，再读取该结构的成员的值。

fish yu=new fish{xiaoyu,10,20.5};
    cout<<yu.name<<endl;
    cout<<yu.weight<<endl;
    cout<<yu.length<<endl;

16.程序清单4.6指出了混合输入数字和一行字符串存储的问题，如果将下面的代码：

`cin.getline(adress,80);`替换为：将对程序带来什么影响？  
使用cin>>address 将使得程序跳过空白，直到找到给空白字符为止。然后它将读取字符，直到再次遇到空白为止。因此，它将跳过数字输入的换行符，从未避免这种问题。另一方面，它值读取一个单词，而不是整行。`cin>>address;`

17.声明一个vector对象和一个array对象，他们都包含10个string对象。指出所需的头文件，但不要使用using，使用const来指定要包含的字符串对象数。

#include<vector>
    #include<array>
    #include<string>
    const int str_num=10;
    std::vector<std::string>vstr(str_num);
    std::array<<std::string,str_num>astr;

## **三、编程练习** ##

1.编写一个c++程序，如下述输出示例的那样请求并显示信息：

`What is your first name? Betty Sue`  
`What is your last name? Yewe`  
`What letter grade do you deserve? B`  
`What is your age? 22`  
`Name:Yewe,Betty Sue`  
`Grade:C`  
`Age:22`

(注意，该程序应该接受的名字包含多个单词。另外，程序将向下调整成绩，即向上调一个字母。假设用户请求A、B或C，所以不必担心D和F之间的空档。)

#include<iostream>
    #include<string>
    int main()
    {
        using namespace std;
        cout << "What your first name? ";
        string first_name;
        getline(cin,first_name) ;
    
        cout << "What your last name? ";
        string last_name;
        getline(cin,last_name);
    
        cout << "What letter grade do you deserve? ";
        char  my_grade;
        cin >> my_grade ;
    
        cout << "What is you age? ";
        int age;
        cin >> age ;
    
        cout << "Name: " << last_name << "," << first_name << endl;
        cout << "Grade: " << ++my_grade<< endl;
        cout << "Age: " << age << endl;
    
        system("pause");
        return 0;
    }

2.修改程序清单4.4，使用C ++ string类而不是char数组。

#include <iostream>
    #include<string>
    int main()
    {
        using namespace std;
        string name;
        string dessert;
    
        cout << "Enter your name:\n";
        getline(cin, name);  // reads through newline
        cout << "Enter your favorite dessert:\n";
        getline(cin,dessert);
        cout << "I have some delicious " << dessert;
        cout << " for you, " << name << ".\n";
    
        system("pause");
        return 0;
    }

3.编写一个程序，他要求用户首先输入其名，然后输入其姓;然后程序使用一个逗号和一个空格将姓和名组合起来，并存储和显示结合效果，请使用char数组和头文件cstring中的函数。下面是该程序的运行时的情形：

`Enter your first name: Flip`  
`Enter your last name: Fleaming`  
`Here's the information in a single string: Fleming, Flip`

#include<iostream>
    #include<cstring>
    //#pragma warning(disable:4996)  //vs2017需要加上这句话，忽略4996警告
    const int Strlen = 20;
    int main()
    {
        using namespace std;
        char first_name[Strlen];
        char last_name[Strlen];
        char full_name[2 * Strlen];
    
        cout << "Enter your first name: ";
        cin.get(first_name,Strlen).get();
    
        cout << "Enter your last name:";
        cin.get(last_name,Strlen).get();
    
        strcpy(full_name,last_name);
        strcat(full_name,", ");
        strcat(full_name, first_name);
    
        cout << "Here's the information in a single string: " << full_name << endl;
        system("pause");
        return 0;
    }

4.编写一个程序，他要求用户首先输入其名，然后输入其姓;然后程序使用一个逗号和一个空格将姓和名组合起来，并存储和显示结合效果，请使用string对象和文件string中的函数。下面是该程序的运行时的情形：

`Enter your first name: Flip`  
`Enter your last name: Fleaming`  
`Here's the information in a single string: Fleming, Flip`

#include<iostream>
    #include<string>
    int main()
    {
        using namespace std;
        string first_name;
        string last_name;
        string full_name;
    
        cout << "Enter your first name: ";
        getline(cin,first_name);
    
        cout << "Enter your last name:";
        getline(cin, last_name);
    
        full_name = last_name + ", " + first_name;
    
        cout << "Here's the information in a single string: " << full_name << endl;
        system("pause");
        return 0;
    }

5.结构CandyBar包含3个成员。第一个成员存储了糖块的品牌；第二个成员存储糖块的重量（可以有小数）；第三个成员存储了糖的卡路里含量（整数）。请编写一个程序，声明这个结构，创建一个名为snack的CandBar变量，并将其成员分别初始化为“Mocha Munch”、2.3和350。初始化在声明snack时进行。最后，程序显示snack变量的内容。

#include<iostream>
    #include<string>
    struct CandyBar {
        std::string brand;
        float weight;
        int calorie;
    };
    int main()
    {
        using namespace std;
        CandyBar snack = {"Mocha Munch",2.3,350};
        cout << "brand: " << snack.brand << endl;
        cout << "weight: " << snack.weight << endl;
        cout << "calorie: " << snack.calorie << endl;
    
        system("pause");
        return 0;
    }

6.结构CandyBar包含3个成员，如编程练习5所示。请编写一个程序，创建一个包含3个元素的CandyBar数组，并将他们初始化为所选择的值，然后显示每个结构的内容。

#include<iostream>
    #include<string>
    struct CandyBar {
        std::string brand;
        float weight;
        int calorie;
    };
    int main()
    {
        using namespace std;
        CandyBar snack[3] = {
            { "Mocha Munch",2.3,350 },
            { "Mocha Munch",2.3,350 },
            { "Mocha Munch",2.3,350 }
        };
        for (int i = 0; i < 3; i++)
        {
            cout << "brand: " << snack[i].brand << endl;
            cout << "weight: " << snack[i].weight << endl;
            cout << "calorie: " << snack[i].calorie << endl;
        }
    
        system("pause");
        return 0;
    }

7.William Wingate从事披萨分析服务。对于每个披萨饼，他都需要记录下列信息：

*  披萨饼公司的名称，可以有多个单词组成。
 *  披萨饼的直径
 *  披萨饼的重量  
    请设计一个能够存储这些信息的结构，并编写一个使用这种结构变量的程序。程序将请求用户输入上述信息，然后显示这些信息。请使用cin（或它的方法）和cout。

#include<iostream>
    #include<string>
    struct Pizza {
        std::string company;
        double diameter;
        double weight;
    };
    int main()
    {
        using namespace std;
        Pizza pizza;
        cout << "Please input pizza's company: ";
        getline(cin, pizza.company);
        cout << "Please input pizza's diameter: ";
        cin>>pizza.diameter;
        cout << "Please input pizza's weight: ";
        cin>> pizza.weight;
    
        cout << "Company: " << pizza.company << endl;
        cout << "Diameter: " <<pizza.diameter << endl;
        cout << "Weight: " << pizza.weight<< endl;
    
        system("pause");
        return 0;
    }

8.完成编程练习7，但使用new来为结构动态分配内存，而不是声明一个结构变量。另外，让程序在请求输入披萨名称之前输入披萨直径。

#include<iostream>
    #include<string>
    struct Pizza {
        std::string company;
        double diameter;
        double  weight;
    };
    int main()
    {
        using namespace std;
        Pizza *p=new Pizza;
    
        cout << "Please input p's diameter: ";
        cin >> p->diameter;
        cin.get();
        cout << "Please input p's company: ";
        getline(cin, p->company);
        cout << "Please input p's weight: ";
        cin>>p->weight;
    
        cout << "Company: " << p->company << endl;
        cout << "Diameter: " <<p->diameter << endl;
        cout << "Weight: " << p->weight<< endl;
    
    
        system("pause");
        return 0;
    }

9.完成编程练习6，但使用new来动态分配数组，而不是声明一个包含3个元素的CandyBar的数组。

#include<iostream>
    #include<string>
    struct CandyBar {
        std::string brand;
        double weight;
        int calorie;
    };
    int main()
    {
        using namespace std;
        CandyBar *snack = new CandyBar[3];
        for (int i = 0; i < 3; i++)
            snack[i]={"Mocha Munch", 2.3, 350};
    
        for (int i = 0; i < 3; i++)
        {
            cout << "brand: " << snack[i].brand << endl;
            cout << "weight: " << snack[i].weight << endl;
            cout << "calorie: " << snack[i].calorie << endl;
        }
        delete[] snack;
        system("pause");
        return 0;
    }

10.编写一个程序，让用户输入三次40码跑的成绩（如果你愿意，也可以让用户输入40米跑的成绩），并显示次数和平均成绩。请使用一个array对象来存储数据（如果编译器不支持array类，请使用数组）。

#include<iostream>
    #include<array>
    int main()
    {
        using namespace std;
        array<double, 3>grade;
    
        cout << "Please input your first grade:";
        cin >> grade[0];
        cout << "Please input your second grade:";
        cin >> grade[1];
        cout << "Please input your third grade:";
        cin >> grade[2];
    
        cout << "Average three times:" << (grade[0] + grade[1] + grade[2]) / 3.0 << endl;
        system("pause");
        return 0;
    }

[unsafe]: https://so.csdn.net/so/search?q=unsafe&spm=1001.2101.3001.7020
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