1.1
prog1.cc 文件代码：
int main()
{
return 0;
}
在prog1.cc 文件所在目录下，依次执行下面命令：
➜ Desktop CC prog1.cc
➜ Desktop a.out
➜ Desktop echo $?
0
注：这里prog1.cc 文件所在目录为Desktop；
1.2
prog1.cc 文件代码修改为：
int main()
{
return -1;
}
在prog1.cc 文件所在目录下，依次执行下面命令：
➜ Desktop CC prog1.cc
➜ Desktop a.out
➜ Desktop echo $?
255
注：这里prog1.cc 文件所在目录为Desktop；
1.3
#include <iostream>
int main() {
std::cout << "Hello, World" << std::endl;
return 0;
}
1.4
#include <iostream>
int main() {
std::cout << "Enter two numbers:" << std::endl;
int v1 = 0, v2 = 0;
std::cin >> v1 >> v2;
std::cout << "The product of " << v1 << " and " << v2
<< " is " << v1 * v2 << std::endl;
return 0;
}
1.5
#include <iostream>
int main() {
std::cout << "Enter two numbers:";
std::cout << std::endl;
int v1 = 0, v2 = 0;
std::cin >> v1 >> v2;
std::cout << "The sum of ";
std::cout << v1;
std::cout << " and ";
std::cout << v2;
std::cout << " is ";
std::cout << v1 + v2;
std::cout << std::endl;
return 0;
}
1.6
std::cout << "The sum of " << v1;
<< " and " << v2;
<< " is " << v1 + v2 << std::endl;
不合法，分号表示一个语句的结束。修正方法：
方法一：
std::cout << "The sum of " << v1;
std::cout << " and " << v2;
std::cout << " is " << v1 + v2 << std::endl;
方法二：
std::cout << "The sum of " << v1
<< " and " << v2
<< " is " << v1 + v2 << std::endl;
1.7
#include <iostream>
/*
* 注释对/* */不能嵌套。
* "不能嵌套"几个字会被认为是源码，
* 像剩余程序一样处理
*/
int main() {
return 0;
}
1.8
std::cout << "/*"; // 合法，输出：/*
std::cout << "*/"; // 合法，输出：*/
std::cout << /* "*/" */; // 不合法
// 编译器提示warning: missing terminating '"' character
// 编译器把第一对/* "*/识别为注释界定符；剩余的" */;识别为源码。
std::cout << /* "*/" /* "/*" */; // 合法，输出 /*
// 首（/* "*/）尾（/*" */）为界定符；" /* "为源码
// /* "*/" /* "/*" */整个这句的一开始是界定符/*，编译器把和它匹配的最近*/之间的内
// 容（ "）识别为注释；接着是"，标志着下一个和它匹配的最近"之间的内容（ /* ）是字符
// 串；接着是界定符/*，编译器把和它匹配的最近*/之间的内容（" ）识别为注释。
// 原则：从左往右，就近匹配。
1.9
#include <iostream>
int main() {
int sum = 0, val = 50;
while (val <= 100) {
sum += val;
++val;
}
std::cout << "Sum of 50 to 100 inclusive is "
<< sum << std::endl;
return 0;
}
1.10
#include <iostream>
int main() {
int val = 10;
while (val >= 0) {
std::cout << val << " ";
--val;
}
std::cout << std::endl;
return 0;
}
1.11
#include <iostream>
int main() {
int val1, val2, temp;
std::cout << "Please input two integers";
std::cin >> val1 >> val2;
if (val1 > val2) {
temp = val1;
val1 = val2;
val2 = temp;
}
++val1;
while (val1 < val2) {
std::cout << val1 << " ";
++val1;
}
std::cout << std::endl;
return 0;
}
1.12
#include <iostream>
int main() {
int sum = 0;
// for循环完成-100～+100之间所有整数累加求和
for (int i = -100; i <= 100; ++i)
sum += i;
std::cout << sum << std::endl;
return 0;
}
sum的终值是0
1.13
#include <iostream>
int main() {
int sum = 0;
for (int val = 50; val <= 100; ++val)
sum += val;
std::cout << "Sum of 50 to 100 inclusive is "
<< sum << std::endl;
return 0;
}
#include <iostream>
int main() {
for (int val = 10; val >= 0; --val)
std::cout << val << " ";
std::cout << std::endl;
return 0;
}
#include <iostream>
int main() {
int val1, val2, temp;
std::cout << "Please input two integers";
std::cin >> val1 >> val2;
if (val1 > val2) {
temp = val1;
val1 = val2;
val2 = temp;
}
for (++val1; val1 < val2; ++val1)
std::cout << val1 << " ";
std::cout << std::endl;
return 0;
}
1.14
while (condition)
statement
while 循环的条件判断（condition）语句在每次执行完循环体（statement）语句都会执行，判断是否继续执行循环体。
for (init-statement; condition; expression)
statement
for 循环的初始化语句（init-statement）在循环开始的时候执行一次，之后执行判断语句（condition），若满足条件，则执行循环体（statement），循环体内的语句执行完后紧接着执行表达式（expression），表达式的作用一般是作用判断语句（condition），使循环在有限次内结束，而不是无限循环。当然 init-statement、conditon和expression这三条语句也可以为空语句（分号不可以省略）：
for (;;)
statement
也可以写多条，多条之间用逗号分隔：
#include <iostream>
int main() {
for (int i = 0, j = 0; i < 2, j < 2; ++i, ++j)
std::cout << i << " " << j << '
';
std::cout << std::endl;
return 0;
}
while 循环的优点是书写简单，缺点是程序员可能忘记在循环体（statement）内作用条件判断语句（condition），造成无限循环；for 循环的优点是规范、整洁，不易漏掉作用条件判断（condition）的表达式（expression），缺点是书写稍繁琐。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。
1.15
略
1.16
#include <iostream>
int main() {
int sum = 0, value = 0;
while (std::cin >> value) {
sum += value;
}
std::cout << "Sum is: " << sum << std::endl;
return 0;
}
1.17
如果输入的值都相等，程序输出相等值的个数；如果没有重复值程序则输出每个数字出现次数为1，按一次Enter，输出上一个数字的统计结果为1.
// 测试数据
3 3 3 3
4
// 运行结果
3 occurs 4 times
// 测试数据
5
// 运行结果
4 occurs 1 times
// 测试数据
6
// 运行结果
5 occurs 1 times
// 测试数据
7
// 运行结果
6 occurs 1 times
// 测试数据
8
// 运行结果
7 occurs 1 times
1.18
// 测试数据
100 100 100 100 100 100
1 2 3 4 5 6 7 8
// 运行结果
100 occurs 6 times
1 occurs 1 times
2 occurs 1 times
3 occurs 1 times
4 occurs 1 times
5 occurs 1 times
6 occurs 1 times
7 occurs 1 times
1.19
1.11 已经考虑到该情况。
1.20
C++ Primer 5th source code download
Sales_item.h
/*
* 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
main.cpp
#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;
return 0;
}
Clion IDE :
// 测试数据
0-201-70353-X 4 24.99
// 运行结果
0-201-70353-X 4 99.96 24.99
Process finished with exit code 0
1.21
Sales_item.h 同1.20，main.cpp 内容如下：
#include <iostream>
#include "Sales_item.h"
int main() {
Sales_item item1, item2;
std::cin >> item1 >> item2; // 读取一对交易记录
std::cout << item1 + item2 << std::endl; // 打印它们的和
return 0;
}
Clion IDE :
// 测试数据
0-201-78345-X 3 20.00
0-201-78456-X 2 25.00
// 运行结果
0-201-78345-X 5 110 22
Process finished with exit code 0
1.22
Sales_item.h 同1.20，main.cpp 内容如下：
/*
* 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
*/
#include <iostream>
#include "Sales_item.h"
int main()
{
Sales_item item1, item2;
std::cin >> item1 >> item2;
// first check that item1 and item2 represent the same book
if (item1.isbn() == item2.isbn()) {
std::cout << item1 + item2 << std::endl;
return 0; // indicate success
} else {
std::cerr << "Data must refer to same ISBN"
<< std::endl;
return -1; // indicate failure
}
}
Clion IDE :
// 测试数据1
0-201-78345-X 4 20.00
0-201-78345-X 5 20.00
// 运行结果1
0-201-78345-X 9 195 21.6667
Process finished with exit code 0
// 测试数据2
0-202-78222-Y 2 25.00
0-201-78111-X 2 29.00
// 运行结果2
Data must refer to same ISBN
Process finished with exit code 255
注：程序结束 0 和 255 正好分别对应 return 0 和 return -1.
1.23
#include <iostream>
#include "Sales_item.h"
int main() {
Sales_item currItem, valItem;
if (std::cin >> currItem) {
int cnt = 1;
while (std::cin >> valItem) {
if (valItem.isbn() == currItem.isbn()) {
++cnt;
} else {
std::cout << currItem.isbn() << " occurs " << cnt << " times " << std::endl;
currItem = valItem;
cnt = 1;
}
}
std::cout << currItem.isbn() << " occurs " << cnt << " times " << std::endl;
}
return 0;
}
// 测试数据
0-201-78345-X 4 25.0
0-201-78345-X 1 25.0
0-201-78345-X 2 25.0
0-201-78345-X 9 25.0
0-207-78345-X 9 31.0
0-207-78345-X 3 31.0
0-202-78345-X 3 20.0
0-202-78345-X 3 20.0
// 运行结果
0-201-78345-X occurs 4 times
0-207-78345-X occurs 2 times
// 接着仍可以继续输入测试数据
1.24
将 exercise_23.cpp 编译运行（代码如 1.23），生成可执行程序。
在控制台执行：
Last login: Wed May 29 08:17:52 on console
➜ ~ /Users/xxx/Desktop/exercise_23 </Users/xxx/Desktop/Untitled-1 >/Users/xxx/Desktop/Untitled-2
➜ ~
Untitled-1 文档内容为：
0-201-78345-X 4 25.0
0-201-78345-X 1 25.0
0-201-78345-X 2 25.0
0-201-78345-X 9 25.0
0-207-78345-X 9 31.0
0-207-78345-X 3 31.0
0-202-78345-X 3 20.0
0-202-78345-X 3 20.0
Untitled-2 文档内容为：
0-201-78345-X occurs 4 times
0-207-78345-X occurs 2 times
0-202-78345-X occurs 2 times
注：该题考查书中知识点使用文件重定向(P_{19})
1.25
Sales_item.h 同1.20，main.cpp 内容如下：
#include <iostream>
#include "Sales_item.h"
int main() {
Sales_item total; // 保存下一条交易记录的变量
// 读入第一条交易记录，并确保有数据可以处理
if (std::cin >> total) {
Sales_item trans; // 保存和的变量
// 读入并处理剩余交易记录
while (std::cin >> trans) {
// 如果我们仍在处理相同的书
if (total.isbn() == trans.isbn())
total += trans; // 更新总销售额
else {
// 打印前一本书的结果
std::cout << total << std::endl;
total = trans; // total 现在表示下一本书的销售额
}
}
std::cout << total << std::endl; // 打印最后一本书的结果
} else {
// 没有输入！警告读者
std::cerr << "No data?!" << std::endl;
return -1; // 表示失败
}
return 0;
}
// 测试数据
0-201-78345-X 4 25.0
0-201-78345-X 1 25.0
0-201-78345-X 2 25.0
0-201-78345-X 9 25.0
0-207-78345-X 9 31.0
0-207-78345-X 3 31.0
0-202-78345-X 3 20.0
0-202-78345-X 3 20.0
// 运行结果
0-201-78345-X 16 400 25
0-207-78345-X 12 372 31