C++ Primer第一章习题答案

  • 练习1.3
#include <iostream>
int main() {
    std::cout << "Hello World" << std::endl;
    system( "Pause" );
    return 0;
}
  • 练习1.4
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#include <iostream>
int main() {
    int v1, v2;
    std::cout << "Enter two numbers：" << std::endl;
    std::cin >> v1 >> v2;
    std::cout << "The product of "<<v1<<" and "<<v2<<" is " << v1*v2<<std::endl;
    system( "Pause" );
    return 0;
}
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  • 练习1.9
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#include <iostream>
int main() {
int sum=0, i=50;
while( i<=100 )
{
    sum += i;
    ++i;
}
std::cout << "Sum of 50 to 100 inclusive is " << sum<<std::endl;
system( "Pause" );
return 0;
}
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  • 练习1.10
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#include <iostream>
int main() {
int  i=10;
std::cout << "The descending order from 10 to 0 is  ";
while( i>=0 )
{
　　std::cout << i<<" " ;
　　--i;
}
std::cout  << std::endl;
system( "Pause" );
return 0;
}
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  • 练习1.11
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#include <iostream>
int main() {
int  temp=0,v1,v2;
std::cout << "Enter two numbers：" ;
std::cin >> v1 >> v2;
if( v1>v2 )
{
    temp = v2;
    v2 = v1;
    v1 = temp;
}
std::cout <<v1 << " to " << v2 <<"  included  " ;
++v1;
while(v1<v2)
{
    std::cout << v1<<" ";
    ++v1;
}
std::cout  << std::endl;
system( "Pause" );
return 0;
}
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  •  练习1.12
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#include <iostream>
int main()
{
    int sum = 0;
    for( int i = -100; i <=100; ++i )
    {
        sum += i;
    }
    std::cout <<"Sum is "<<sum<<std::endl;
    system( "Pause" );
    return 0;
}
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Sum is 0

  • 练习1.13

（50-100的和）

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#include <iostream>
int main()
{
    int sum = 0;
    for( int i = 50; i <= 100; ++i )
    {
        sum += i;
    }
    std::cout << "Sum of 50 to 100 inclusive is " << sum << std::endl;
    system( "Pause" );
    return 0;
}
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（递减打出10-0）

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#include <iostream>
int main()
{
    std::cout << "The descending order from 10 to 0 is  ";
    for( int i = 10; i >0; --i )
    {
        std::cout << i << " ";
    }
    std::cout << std::endl;
    system( "Pause" );
    return 0;
}
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（输入2个整数，打印出范围内所有整数）

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#include <iostream>
int main()
{
    int  temp = 0, v1, v2;
    std::cout << "Enter two numbers：";
    std::cin >> v1 >> v2;
    if( v1>v2 )
    {
        temp = v2;
        v2 = v1;
        v1 = temp;
    }
    std::cout << v1 << " to " << v2 << "  included  ";for( ++v1; v1 < v2; v1++ )
    {
        std::cout << v1 << " ";
    }
    std::cout << std::endl;
    system( "Pause" );
    return 0;
}
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  • 练习1.14

while 循环适合循环次数不确定的情景；for 循环适合循环次数事先已知。

  • 练习1.16
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#include <iostream>
int main() {
    int sum = 0, value = 0;
    while (std::cin >> value) {
        sum += value;
    }
    std::cout << "Sum is: " << sum << std::endl;
    return 0;
}
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  • 练习1.20

Sales_item.h

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/*
* This file contains code from "C++ Primer, Fifth Edition", by Stanley B.
* Lippman, Josee Lajoie, and Barbara E. Moo, and is covered under the
* copyright and warranty notices given in that book:
*
* "Copyright (c) 2013 by Objectwrite, Inc., Josee Lajoie, and Barbara E. Moo."
*
*
* "The authors and publisher have taken care in the preparation of this book,
* but make no expressed or implied warranty of any kind and assume no
* responsibility for errors or omissions. No liability is assumed for
* incidental or consequential damages in connection with or arising out of the
* use of the information or programs contained herein."
*
* Permission is granted for this code to be used for educational purposes in
* association with the book, given proper citation if and when posted or
* reproduced.Any commercial use of this code requires the explicit written
* permission of the publisher, Addison-Wesley Professional, a division of
* Pearson Education, Inc. Send your request for permission, stating clearly
* what code you would like to use, and in what specific way, to the following
* address:
*
*     Pearson Education, Inc.
*     Rights and Permissions Department
*     One Lake Street
*     Upper Saddle River, NJ  07458
*     Fax: (201) 236-3290
*/
/* This file defines the Sales_item class used in chapter 1.
* The code used in this file will be explained in
* Chapter 7 (Classes) and Chapter 14 (Overloaded Operators)
* Readers shouldn't try to understand the code in this file
* until they have read those chapters.
*/
#ifndef SALESITEM_H
// we're here only if SALESITEM_H has not yet been defined 
#define SALESITEM_H
// Definition of Sales_item class and related functions goes here
#include <iostream>
#include <string>

class Sales_item
{
    // these declarations are explained section 7.2.1, p. 270 
    // and in chapter 14, pages 557, 558, 561
    friend std::istream& operator >> ( std::istream&, Sales_item& );
    friend std::ostream& operator<<( std::ostream&, const Sales_item& );
    friend bool operator<( const Sales_item&, const Sales_item& );
    friend bool operator==( const Sales_item&, const Sales_item& );
public:
    // constructors are explained in section 7.1.4, pages 262 - 265
    // default constructor needed to initialize members of built-in type
    Sales_item() : units_sold( 0 ), revenue( 0.0 ) {}
    Sales_item( const std::string &book ) :
        bookNo( book ), units_sold( 0 ), revenue( 0.0 )
    {}
    Sales_item( std::istream &is ) { is >> *this; }
public:
    // operations on Sales_item objects
    // member binary operator: left-hand operand bound to implicit this pointer
    Sales_item& operator+=( const Sales_item& );

    // operations on Sales_item objects
    std::string isbn() const { return bookNo; }
    double avg_price() const;
    // private members as before
private:
    std::string bookNo;      // implicitly initialized to the empty string
    unsigned units_sold;
    double revenue;
};
// used in chapter 10
inline
bool compareIsbn( const Sales_item &lhs, const Sales_item &rhs )
{
    return lhs.isbn() == rhs.isbn();
}
// nonmember binary operator: must declare a parameter for each operand
Sales_item operator+( const Sales_item&, const Sales_item& );
inline bool
operator==( const Sales_item &lhs, const Sales_item &rhs )
{
    // must be made a friend of Sales_item
    return lhs.units_sold == rhs.units_sold &&
        lhs.revenue == rhs.revenue &&
        lhs.isbn() == rhs.isbn();
}
inline bool
operator!=( const Sales_item &lhs, const Sales_item &rhs )
{
    return !( lhs == rhs ); // != defined in terms of operator==
}

// assumes that both objects refer to the same ISBN
Sales_item& Sales_item::operator+=( const Sales_item& rhs )
{
    units_sold += rhs.units_sold;
    revenue += rhs.revenue;
    return *this;
}
// assumes that both objects refer to the same ISBN
Sales_item
operator+( const Sales_item& lhs, const Sales_item& rhs )
{
    Sales_item ret( lhs );  // copy (|lhs|) into a local object that we'll return
    ret += rhs;           // add in the contents of (|rhs|) 
    return ret;           // return (|ret|) by value
}
std::istream&
operator >> ( std::istream& in, Sales_item& s )
{
    double price;
    in >> s.bookNo >> s.units_sold >> price;
    // check that the inputs succeeded
    if( in )
        s.revenue = s.units_sold * price;
    else
        s = Sales_item();  // input failed: reset object to default state
    return in;
}
std::ostream&
operator<<( std::ostream& out, const Sales_item& s )
{
    out << s.isbn() << " " << s.units_sold << " "
        << s.revenue << " " << s.avg_price();
    return out;
}
double Sales_item::avg_price() const
{
    if( units_sold )
        return revenue / units_sold;
    else
        return 0;
}
#endif
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main.cpp

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#include <iostream>
#include "Sales_item.h"
int main()
{
    Sales_item book;
    //读入ISBN号、售出的册数以及销售价格
    std::cin >> book;
    //写入ISBN、售出的册数、总销售额和平均价格
    std::cout << book << std::endl;
    system( "Pause" );
    return 0;
}
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  • 练习1.21

（Sales_item.h同1.20，代码相同）

 main.cpp

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#include <iostream>
#include "Sales_item.h"
int main()
{
    Sales_item book1,book2;
    //读入ISBN号、售出的册数以及销售价格
    std::cin >> book1>>book2;
    //写入ISBN、售出的册数、总销售额和平均价格
    std::cout << book1+book2 << std::endl;
    system( "Pause" );
    return 0;
}
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  • 练习1.22

（Sales_item.h同1.20，代码相同）

 main.cpp

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#include <iostream>
#include "Sales_item.h"
int main()
{
    Sales_item book,sum_book;
    std::cin >> sum_book;
    while( std::cin >> book )
    {
        sum_book += book;
    }
    std::cout <<sum_book << std::endl;
    system( "Pause" );
    return 0;
}
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  • 练习1.23

（Sales_item.h同1.20，代码相同）

 main.cpp

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#include <iostream>
#include "Sales_item.h"
int main() {
    //currItem作为参照值，valItem后输入值
    Sales_item currItem,valItem;
    //输入值后作为参照值
    if (std::cin>>currItem) {
        int cnt=1;
        //循环获取后续值
        while (std::cin>>valItem) {
            if (currItem.isbn()==valItem.isbn()) {
                ++cnt;
            }else{
                //这里需要先输出，后赋值，否则会影响输出结果
                std::cout << currItem.isbn() << " occurs " << cnt << " times " << std::endl;
                currItem=valItem;
                cnt=1;
            }
        }
        std::cout << currItem.isbn() << " occurs " << cnt << " times " << std::endl;
    }
    return 0;
}
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  • 练习1.25

（Sales_item.h同1.20，代码相同）

 main.cpp

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#include <iostream>
#include "Sales_item.h"
int main()
{
    //有交易记录的变量
    Sales_item total;
    if( std::cin >> total )
    {
        //记录和的变量
        Sales_item trans;
        //循环获取后续值
        while( std::cin >> trans )
        {
            if( total.isbn() == trans.isbn() )
            {
                //更新总销售额
                total += trans;
            }
            else
            {
                //打印前一本书的结果
                std::cout << total << std::endl;
                total = trans;
            }
        }
        std::cout << total << std::endl;
    }
    else
    {
        //没有输入警告
        std::cerr << "No date?" << std::endl;
        return  -1;
    }
    system( "Pause" );
    return 0;
}
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第一章完结啦！

 

posted @   joyfulest  阅读(27)  评论(0)  编辑  收藏  举报
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