1.1
int main()
{
return 0;
}
1.2
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 multiplication of " << v1 << " and " << v2
<< " is " << v1 * v2 << std::endl;
return 0;
}
1.5
#include <iostream>
int main()
{
std::cout << "Enter two numbers:" << std::endl;
int v1 = 0, v2 = 0;
std::cin >> v1 >> v2;
std::cout << "The multiplication 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
不正确
因为 ; 代表一条语句的结束，第二行语句没有输出流对象，所以错误。
std::cout << "The sum of " << v1;
std::cout << " and " << v2;
std::cout << " is " << v1 + v2 << std::endl;
1.7
#include <iostream>
int main()
{
/*
注释测试程序 */
*/
}
1.8
std::cout << "/*"; // 正确
std::cout << "*/"; // 正确
std::cout << /* "*/" */; // 错误
std::cout << /* "*/" /* "/*" */; // 正确
修改
std::cout << /* "*/" */";
1.9
#include <iostream>
int main()
{
int i = 50, result = 0;
while (i <= 100)
{
result += i;
++i;
}
std::cout << result << std::endl;
return 0;
}
1.10
#include <iostream>
int main()
{
int i = 10;
while (i >= 0)
{
std::cout << i << std::endl;
--i;
}
return 0;
}
1.11
#include <iostream>
int main()
{
std::cout << "Please input two numbers: " << std::endl;
int v1, v2;
std::cin >> v1 >> v2;
while (v1 <= v2)
{
std::cout << v1 << " ";
v1++;
}
std::cout << std::endl;
return 0;
}
1.12
将 -100 到 100 之间的数想加，sum 的终值是 0。
1.13
#include <iostream>
int main()
{
int result = 0;
for (int i = 50; i <= 100; ++i)
result += i;
std::cout << result << std::endl;
return 0;
}
#include <iostream>
int main()
{
for (int i = 10; i >= 0; --i)
std::cout << i << " ";
std::cout << std::endl;
return 0;
}
#include <iostream>
int main()
{
std::cout << "Please input two numbers: " << std::endl;
int v1, v2;
std::cin >> v1 >> v2;
for (; v1 <= v2; v1++)
std::cout << v1 << " ";
std::cout << std::endl;
return 0;
}
1.14
for 和 while 功能上是等价的，优缺点根据实际情况具体分析。
1.16
#include <iostream>
int main()
{
int num = 0, result = 0;
while (std::cin >> num)
{
result += num;
}
std::cout << result << std::endl;
return 0;
}
1.17
输出当前值出现的次数。没有重复值，输出次数结果都为1。
1.18
1.19
#include <iostream>
int main()
{
std::cout << "Please input two numbers: " << std::endl;
int v1, v2;
std::cin >> v1 >> v2;
if (v1 > v2)
{
int tmp = v1;
v1 = v2;
v2 = tmp;
}
int result = 0;
for (; v1 <= v2; v1++)
result += v1;
std::cout << result << std::endl;
return 0;
}
1.20
Sales_item.h
#ifndef SALESITEM_H
#define SALESITEM_H
#include <iostream>
#include <string>
class Sales_item
{
public:
Sales_item(const std::string& book) :isbn(book), units_sold(0), revenue(0.0) {}
Sales_item(std::istream& is) { is >> *this; }
friend std::istream& operator>>(std::istream&, Sales_item&);
friend std::ostream& operator<<(std::ostream&, const Sales_item&);
public:
Sales_item& operator+=(const Sales_item&);
public:
double avg_price() const;
bool same_isbn(const Sales_item& rhs)const
{
return isbn == rhs.isbn;
}
Sales_item() :units_sold(0), revenue(0.0) {}
public:
std::string isbn;
unsigned units_sold;
double revenue;
};
using std::istream;
using std::ostream;
Sales_item operator+(const Sales_item&, const Sales_item&);
inline bool operator==(const Sales_item& lhs, const Sales_item& rhs)
{
return lhs.units_sold == rhs.units_sold && lhs.revenue == rhs.revenue && lhs.same_isbn(rhs);
}
inline bool operator!=(const Sales_item& lhs, const Sales_item& rhs)
{
return !(lhs == rhs);
}
inline Sales_item& Sales_item::operator +=(const Sales_item& rhs)
{
units_sold += rhs.units_sold;
revenue += rhs.revenue;
return *this;
}
inline Sales_item operator+(const Sales_item& lhs, const Sales_item& rhs)
{
Sales_item ret(lhs);
ret += rhs;
return ret;
}
inline istream& operator>>(istream& in, Sales_item& s)
{
double price;
in >> s.isbn >> s.units_sold >> price;
if (in)
s.revenue = s.units_sold * price;
else
s = Sales_item();
return in;
}
inline ostream& operator<<(ostream& out, const Sales_item& s)
{
out << s.isbn << "\t" << s.units_sold << "\t" << s.revenue << "\t" << s.avg_price();
return out;
}
inline double Sales_item::avg_price() const
{
if (units_sold)
return revenue / units_sold;
else
return 0;
}
#endif
#include "Sales_item.h"
int main()
{
Sales_item item;
std::cin >> item;
std::cout << item << std::endl;
}
1.21
#include "Sales_item.h"
int main()
{
Sales_item item1, item2;
std::cin >> item1 >> item2;
std::cout << (item1 + item2) << std::endl;
}
1.22
#include "Sales_item.h"
int main()
{
Sales_item item, result;
if (std::cin >> item)
{
result = item;
while (std::cin >> item)
{
result += item;
}
}
std::cout << result << std::endl;
return 0;
}
1.23
#include "Sales_item.h"
int main()
{
Sales_item item1, item2;
int cnt = 1;
if (std::cin >> item1)
{
while (std::cin >> item2)
{
if (item1.same_isbn(item2))
{
cnt++;
}
else {
std::cout << item1.isbn << " has " << cnt << " times." << std::endl;
item1 = item2;
cnt = 1;
}
}
std::cout << item1.isbn << " has " << cnt << " times." << std::endl;
}
return 0;
}
1.24
1.25
#include "Sales_item.h"
int main()
{
Sales_item total;
if (std::cin >> total)
{
Sales_item trans;
while (std::cin >> trans)
{
if (total.same_isbn(trans))
total += trans;
else
{
std::cout << total << std::endl;
total = trans;
}
}
std::cout << total << std::endl;
}
else {
std::cerr << "No data?!" << std::endl;
return -1;
}
return 0;
}
