文章目录

第四章
- - 4.21
  - 4.22
第五章
- - 5.12
  - 5.14
  - 5.17
  - 5.20
  - 5.21
  - 5.25
第六章
- - 6.3
  - 6.4
  - 6.5
  - 6.9
  - 6.10
  - 6.12
  - 6.17
  - 6.21
  - 6.22
  - 6.23
  - 6.25
  - 6.26
  - 6.27
  - 6.32
  - 6.33
  - 6.56
第七章
- - 7.1
  - 7.2
  - 7.3
  - 7.4 7.5
  - 7.6
  - 7.7
  - 7.8
  - 7.11
  - 7.12
  - 7.13
  - 7.14
  - 7.15
  - 7.26
  - 7.27
  - 7.31
  - 7.32
  - 7.41
  - 7.53

第四章

4.21

#include<iostream>
using namespace std;
#include<vector>

int main()
{
    
    
	vector<int>v;
	for (int i = 0; i < 10; i++) {
    
    
		v.push_back(i);
	}

	for (auto &val : v) {
    
    
		val = ((val % 2 != 0) ? val * 2 : val);
	}
	for (auto val2 : v) {
    
    
		cout << val2 << " ";
	}
	cout << endl;
	system("pause");
	return 0;
}

4.22

#include<iostream>
using namespace std;
#include<string>

int main()
{
    
    
	int grade = 0;
	while (cin >> grade && grade<101 && grade>=0) {
    
    
		string finalgrade = (grade > 90) ? "high pass"
			: (grade < 75 && grade>60) ? "low pass"
			: (grade < 60) ? "fail" : "pass";
		cout << finalgrade << endl;
	}

	system("pause");
	return 0;
}

#include<iostream>
using namespace std;
#include<string>

int main()
{
    
    
	int grade = 0;
	while (cin >> grade && grade<101 && grade>=0) {
    
    
		if (grade > 90) {
    
    
			cout << "heigh pass" << endl;
		}
		else if(grade > 75) {
    
    
			cout << "pass" << endl;
		}
		else if (grade > 60) {
    
    
			cout << "low pass";
		}
		else {
    
    
			cout << "fail";
		}
	}

	system("pause");
	return 0;
}

第五章

5.12

#include<iostream>
using namespace std;

int main()
{
    
    
	int ffcnt = 0, ficnt = 0, flcnt = 0;
	char ch;

	while (cin >> ch)
	{
    
    
		if (ch == 'f')
		{
    
    
			while (cin >> ch)
			{
    
    
				switch (ch)
				{
    
    
				case 'f':
					++ffcnt;
					break;
				case 'l':
					++flcnt;
					break;
				case 'i':
					++ficnt;
					break;
				default:
					break;
				}
				break;
			}
		}
	}
	cout << "ff: " << ffcnt << endl;
	cout << "fl: " << flcnt << endl;
	cout << "fi: " << ficnt << endl;
}

5.14

#include<iostream>
using namespace std;
#include<cstring>

int main()
{
    
    
	string currstring="",maxstring="",nowstring="";
	int currnum = 1, maxnum = 0;

	while (cin >> currstring)
	{
    
    
		if (currstring == nowstring)
		{
    
    
			++currnum;
			if (currnum > maxnum)
			{
    
    
				maxnum = currnum;
				maxstring = currstring;
			}
		}
		else
		{
    
    
			nowstring = currstring;
			currnum = 1;
		}
	}
	cout << maxstring << " " << "number is:" << maxnum << endl;
}

5.17

#include<iostream>
using namespace std;
#include<vector>

int main()
{
    
    
	vector<int>v1={
    
    0,1,1,2};
	vector<int>v2={
    
    0,1,1,2,3,5,8};

	vector<int>::iterator it1 = v1.begin(), it2 = v2.begin();
	for (; it1 != v1.end() && it2 != v2.end(); it1++, it2++)
	{
    
    
		if (*it1 != *it2)
		{
    
    
			cout << "无关" << endl;
		}
	}

	if (it1 == v1.end())
	{
    
    
		cout << "v1 是 v2的前缀" << endl;
	}
	if(it2==v2.end())
	{
    
    
		cout << "v2 是 v1的前缀" << endl;
	}


	system("pause");
	return 0;
}

5.20

#include<iostream>
using namespace std;
#include<cstring>

int main()
{
    
    
	string currstring, nowstring;
	bool flag = true;

	while (cin >> currstring)
	{
    
    
		if (currstring == nowstring)
		{
    
    
			flag = false;
			cout << "重复单词:" << currstring << endl;
			break;
		}
		nowstring = currstring;
	}
	if (flag)
	{
    
    
		cout << "无重复" << endl;
	}


	system("pause");
	return 0;
}

5.21

#include<iostream>
using namespace std;
#include<cstring>
#include<cctype>

int main()
{
    
    
	string currstring, nowstring;
	bool flag = true;

	while (cin >> currstring)
	{
    
    
		if (!isupper(currstring[0]))
			continue;

		if (currstring == nowstring)
		{
    
    
			flag = false;
			cout << "重复单词:" << currstring << endl;
			break;
		}
		nowstring = currstring;
	}
	if (flag)
	{
    
    
		cout << "无重复" << endl;
	}


	system("pause");
	return 0;
}

5.25

#include<iostream>
using namespace std;
#include<stdexcept>

int main()
{
    
    
	int a = 0, b = 0;
	while (cin >> a >> b)
	{
    
    
		try
		{
    
    
			if (b == 0)
			{
    
    
				throw runtime_error("除数不能为0");
			}
			cout << a / b << endl;
		}
		catch (runtime_error chushu_is_zero)
		{
    
    
			cout << chushu_is_zero.what() << endl;
			cout<< "是否重新输入y or n" << endl;
			char c;
			cin >> c;
			if (!cin || c == 'n')
			{
    
    
				break;
			}
		}
	}
	system("pause");
	return 0;
}

第六章

6.3

#include<iostream>
using namespace std;

int fact(int a)
{
    
    
	int sum = 1;
	while (a > 1)
	{
    
    
		sum *= a;
		--a;
	}
	return sum;
}

int main()
{
    
    
	int i = fact(5);
	cout << i << endl;

	system("pause");
	return 0;
}

6.4

同上

6.5

#include<iostream>
using namespace std;
#include<cmath>

int fact(int a)
{
    
    
	int num = abs(a);
	return num;
}

int main()
{
    
    
	int i = fact(-5);
	cout << i << endl;

	system("pause");
	return 0;
}

6.9

Chapter6.h

#pragma once
int fact(int a);

fact.cpp

#include"Chapter6.h"
using namespace std;

int fact(int a)
{
    
    
	int sum = 1;
	while (a > 1)
	{
    
    
		sum *= a;
		--a;
	}
	return sum;
}

main.cpp

#include<iostream>
using namespace std;
#include"Chapter6.h"

int main()
{
    
    
	
	cout << fact(5) << endl;

	system("pause");
	return 0;
}

6.10

#include<iostream>
using namespace std;

void exchange(int* p, int* q)
{
    
    
	int a = 0;
	a = *p;
	*p = *q;
	*q = a;

}

int main()
{
    
    
	int a = 10, b = 8;
	exchange(&a, &b);
	cout << "a= " << a << " " << "b= " << b << endl;

	system("pause");
	return 0;
}

6.12

#include<iostream>
using namespace std;

void exchange(int &p, int &q)
{
    
    
	int temp = 0;
	temp = p;
	p = q;
	q = temp;
}

int main()
{
    
    
	int a = 10, b = 8;
	exchange(a, b);
	cout << "a= " << a << " " << "b= " << b << endl;

	system("pause");
	return 0;
}

6.17

#include<iostream>
using namespace std;
#include<cstring>
#include<cctype>

bool have_da(const string& s)
{
    
    
	for (char val : s)
	{
    
    
		if (isupper(val))
		{
    
    
			return true;
		}
	}
	return false;
}

void tolow(string& s)
{
    
    
	if (have_da(s))
	{
    
    
		for (char &val : s)
		{
    
    
			val = tolower(val);
		}
	}
}

int main()
{
    
    
	string s("Hello Wrold");
	bool flag;
	flag = have_da(s);
	if (flag)
	{
    
    
		cout << "有大写字母" << endl;
		tolow(s);
		cout << "转化为小写字母后：" << s << endl;
	}
	else
	{
    
    
		cout << "无大写字母" << endl;
	}

	system("pause");
	return 0;
}

6.21

#include<iostream>
using namespace std;
#include<ctime>
#include<cstdlib>

int compare(int a, const int* b)
{
    
    
	if (a > *b)
	{
    
    
		return a;
	}
	else
	{
    
    
		return *b;
	}
}

int main()
{
    
    
	int a=0, b=0;
	srand((unsigned int)time(NULL));
	cout << "输入第一个数" << endl;
	cin >> a;
	b = rand() % 100 + 1;
	int max = compare(a, &b);
	cout << "a= " << a << " " << "b= " << b << endl;
	cout << "较大的数：" << max << endl;

	system("pause");
	return 0;
}

6.22

#include<iostream>
using namespace std;

void swap1(int* q, int* p)
{
    
    
	int* temp;
	temp = q;
	q = p;
	p = temp;//交换指针地址，只是临时交换，实参没有改变，所以值和地址都没有变
}

void swap2(int* q, int* p)
{
    
    
	int temp;
	temp = *q;
	*q = *p;
	*p = temp;//指针值传递，内部解引用交换了值
}

void swap3(int*& q, int*& p)
{
    
    
	int* temp;
	temp = q;
	q = p;
	p = temp; //引用方式，也改变了实参的地址和值
}

int main()
{
    
    
	int a = 10, b = 100;
	int* q = &a, * p = &b;
	cout << "before: " << endl;
	cout << "q= " << q << " " << "p= " << p << endl;
	cout << "q的值: " << *q << " " << "p的值: " << *p << endl;
	cout << "after:" << endl;
	swap1(q,p);
	cout << "q= " << q << " " << "p= " << p << endl;
	cout << "q的值: " << *q << " " << "p的值: " << *p << endl;

	a = 10, b = 100;
	q = &a, p = &b;
	cout << "before: " << endl;
	cout << "q= " << q << " " << "p= " << p << endl;
	cout << "q的值: " << *q << " " << "p的值: " << *p << endl;
	cout << "after:" << endl;
	swap2(q,p);
	cout << "q= " << q << " " << "p= " << p << endl;
	cout << "q的值: " << *q << " " << "p的值: " << *p << endl;

	a = 10, b = 100;
	q = &a, p = &b;
	cout << "before: " << endl;
	cout << "q= " << q << " " << "p= " << p << endl;
	cout << "q的值: " << *q << " " << "p的值: " << *p << endl;
	cout << "after:" << endl;
	swap3(q,p);
	cout << "q= " << q << " " << "p= " << p << endl;
	cout << "q的值: " << *q << " " << "p的值: " << *p << endl;

	system("pause");
	return 0;
}

6.23

#include<iostream>
using namespace std;

void print1(const int arr[])
{
    
    
	cout << *arr << endl;
}

void print2(const int* begin, const int* end)
{
    
    
	while (begin != end)
	{
    
    
		cout << *begin << " ";
		++begin;
	}
	cout << endl;
}

void print3(const int* arr, size_t size)
{
    
    
	for (size_t i = 0; i < size; i++)
	{
    
    
		cout << arr[i] << " ";
	}
	cout << endl;
}

int main()
{
    
    
	int i = 0, j[2] = {
    
     0,1 };
	print1(&i);
	print1(j);

	int* beg = begin(j);
	int* en = end(j);
	print2(beg,en);

	size_t size = sizeof(j)/sizeof(*j);
	print3(j, size);
	print3(&i, 1);

	system("pause");
	return 0;
}

6.25

#include<iostream>
using namespace std;
#include<cstring>

int main(int argc,char**argv)
{
    
    
	string str;
	for (int i = 0; i != argc; ++i)
	{
    
    
		str += argv[i];
	}
	cout << str << endl;

	system("pause");
	return 0;
}

调试->调试属性->调试->命令参数添加自定义命令

argv[0]=你保存程序的名字

在这里插入图片描述

6.26

#include<iostream>
using namespace std;
#include<cstring>

int main(int argc,char**argv)
{
	for (int i = 0; i != argc; ++i)
	{
		cout << "argv[" << i << "]=" << argv[i] << endl;
	}
	
	system("pause");
	return 0;
}

在这里插入图片描述

6.27

#include<iostream>
using namespace std;

int count(initializer_list<int> l1)
{
    
    
	int sum = 0;
	for (auto val : l1)
	{
    
    
		sum += val;
	}
	return sum;
}

int main()
{
    
    
	cout << count({
    
     1,2,3 }) << endl;
	cout << count({
    
     1,2,3,4,5,6 }) << endl;
	
	system("pause");
	return 0;
}

6.32

#include<iostream>
using namespace std;

int& get(int* arry, int index)
{
    
    
	return arry[index];
}

int main()
{
    
    
	int ia[10];
	for (int i = 0; i != 10; ++i)
	{
    
    
		get(ia, i) = i;
	}
	for (int val : ia)
	{
    
    
		cout << val << " ";
	}
	cout << endl;

	system("pause");
	return 0;
}

6.33

#include<iostream>
using namespace std;
#include<vector>

void print(vector<int> &v, vector<int>::iterator it)
{
    
    
	if (!v.empty())
	{
    
    
		if (it != v.end())
		{
    
    
			cout << *it << " ";
			print(v, it+1);
		}
		cout << endl;
	}
	else
	{
    
    
		return;
	}
}

int main()
{
    
    
	vector<int> v = {
    
     0,1,2,3,4,5,6,7,8,9 };
	auto it = v.begin();
	auto itend = v.end();
	print(v, it);

	system("pause");
	return 0;
}

6.56

#include<iostream>
using namespace std;
#include<vector>

int f1(int a, int b)
{
    
    
	return a + b;
}
int f2(int a, int b)
{
    
    
	return a - b;
}int f3(int a, int b)
{
    
    
	return a *b;
}int f4(int a, int b)
{
    
    
	return a / b;
}

int main()
{
    
    
	//decltype(f1)* p1 = f1, * p2 = f2, * p3 = f3, * p4 = f4;
	//vector<decltype(f1)*>v{ p1,p2,p3,p4 };
	vector<decltype(f1)*>v{
    
     f1,f2,f3,f4 };

	for (auto val : v)
	{
    
    
		cout << val(1,2) << endl;
	}
}

第七章

7.1

Salse_data.h

#pragma once

#include<iostream>
#include<string>

class Sales_data
{
    
    
    friend istream& operator>>(std::istream&, Sales_data&);
    friend ostream& operator<<(std::ostream&, const  Sales_data&);

public:
    Sales_data() = default;
    Sales_data(const std::string& book) : bookNo(book), units_sold(0), sellingprice(0.0), saleprice(0.0), discount(0.0) {
    
    }
    Sales_data(std::istream& is)
    {
    
    
        is >> *this;
    }

public:
    Sales_data& operator+=(const Sales_data& rhs)
    {
    
    
        units_sold += rhs.units_sold;
        saleprice = (rhs.saleprice * rhs.units_sold + saleprice * units_sold) / (rhs.units_sold + units_sold);
        sellingprice = (rhs.sellingprice * rhs.units_sold + sellingprice * units_sold) / (rhs.units_sold + units_sold);
        if (sellingprice != 0)
        {
    
    
            discount = saleprice / sellingprice;
        }
        return *this;
    }

    string isbn() const
    {
    
    
        return bookNo;
    }

private:
    string bookNo;
    int units_sold = 0;
    double sellingprice = 0.0;
    double saleprice = 0.0;
    double discount = 0.0;

};

inline bool compareIsbn(const Sales_data& lhs, const Sales_data& rhs)
{
    
    
    return lhs.isbn() == rhs.isbn();
}





istream& operator>>(std::istream& in, Sales_data& s)
{
    
    
    double price;
    in >> s.bookNo >> s.units_sold >> s.sellingprice >> s.saleprice;

    if (in && s.sellingprice != 0)
        s.discount = s.saleprice / s.sellingprice;
    else
        s = Sales_data();  // input failed: reset object to default state
    return in;
}

ostream& operator<<(std::ostream& out, const Sales_data& s)
{
    
    
    out << s.isbn() << " " << s.units_sold << " " << s.sellingprice << " " << s.saleprice << " " << s.discount;
    return out;
}

main.cpp

#include<iostream>
using namespace std;
#include"Sales_data.h"


int main()
{
    
    
	Sales_data total;
	Sales_data trans;

	cout << "请输入：（ISBN，销售量，原价，实际售价）" << endl;

	if (cin >> total)
	{
    
    
		while (cin >> trans)
		{
    
    
			if (compareIsbn(total, trans))
			{
    
    
				total += trans;
			}
			else
			{
    
    
				cout << "ISBN ，销售量， 原价，平均销售价格，折扣" << total << endl;
				total = trans;
			}
		}
		cout << "ISBN ，销售量， 原价，平均销售价格,折扣" << total << endl;
	}
	else
	{
    
    
		cout << "无数据" << endl;
	}


	system("pause");
	return 0;
}

7.2

Salse_data.h

#pragma once

#include<iostream>
#include<string>

class Sales_data
{
    
    
    friend istream& operator>>(std::istream&, Sales_data&);
    friend ostream& operator<<(std::ostream&, const  Sales_data&);

public:
    Sales_data() = default;
    Sales_data(const std::string& book) : bookNo(book), units_sold(0), sellingprice(0.0), saleprice(0.0), discount(0.0) {
    
    }
    Sales_data(std::istream& is)
    {
    
    
        is >> *this;
    }

public:
    Sales_data& combine(const Sales_data& rhs)
    {
    
    
        units_sold += rhs.units_sold;
        saleprice = (rhs.saleprice * rhs.units_sold + saleprice * units_sold) / (rhs.units_sold + units_sold);
        sellingprice = (rhs.sellingprice * rhs.units_sold + sellingprice * units_sold) / (rhs.units_sold + units_sold);
        if (sellingprice != 0)
        {
    
    
            discount = saleprice / sellingprice;
        }
        return *this;
    }

    string isbn() const//只读不写
    {
    
    
        return bookNo;
    }

private:
    string bookNo;
    int units_sold = 0;
    double sellingprice = 0.0;
    double saleprice = 0.0;
    double discount = 0.0;

};

inline bool compareIsbn(const Sales_data& lhs, const Sales_data& rhs)
{
    
    
    return lhs.isbn() == rhs.isbn();
}



istream& operator>>(std::istream& in, Sales_data& s)
{
    
    
    double price;
    in >> s.bookNo >> s.units_sold >> s.sellingprice >> s.saleprice;

    if (in && s.sellingprice != 0)
        s.discount = s.saleprice / s.sellingprice;
    else
        s = Sales_data();  // input failed: reset object to default state
    return in;
}

ostream& operator<<(std::ostream& out, const Sales_data& s)
{
    
    
    out << s.isbn() << " " << s.units_sold << " " << s.sellingprice << " " << s.saleprice << " " << s.discount;
    return out;
}

7.3

main.cpp

#include<iostream>
using namespace std;
#include"Sales_data.h"


int main()
{
    
    
	Sales_data total;
	Sales_data trans;

	cout << "请输入：（ISBN，销售量，原价，实际售价）" << endl;

	if (cin >> total)
	{
    
    
		while (cin >> trans)
		{
    
    
			if (compareIsbn(total, trans))
			{
    
    
				total.combine(trans);
			}
			else
			{
    
    
				cout << "ISBN ，销售量， 原价，平均销售价格，折扣" << total << endl;
				total = trans;
			}
		}
		cout << "ISBN ，销售量， 原价，平均销售价格,折扣" << total << endl;
	}
	else
	{
    
    
		cout << "无数据" << endl;
	}


	system("pause");
	return 0;
}

7.4 7.5

#include<iostream>
using namespace std;
#include<cstring>

class Person
{
    
    
public:
	string getname ()const
	{
    
    
		return name;
	}
	string getaddress()const
	{
    
    
		return address;
	}

private:
	string name;
	string address;
};

int main()
{
    
    

	system("pause");
	return 0;
}

7.6

Sales_data add(const Sales_data& lhs, const Sales_data& rhs)
{
    
    
	Sales_data sum = lhs;
	sum.combine(rhs);
	return sum;
}
istream& read(istream& is, Sales_data& item)
{
    
    
	is >> item.bookNo >> item.units_sold >> item.sellingprice >> item.saleprice;
	return is;
}
ostream& print(ostream& os, const Sales_data& item)
{
    
    
	os << item.isbn() << " " << item.units_sold << " " << item.sellingprice << " " << item.saleprice << " " << item.discount;
}

7.7

Saales_data.h

#pragma once

#include<iostream>
#include<string>

class Sales_data
{
    
    
    friend istream& read(istream& is, Sales_data& item);
    friend ostream& print(ostream& os, const Sales_data& item);


//public:
//    Sales_data() = default;
//    Sales_data(const std::string& book) : bookNo(book), units_sold(0), sellingprice(0.0), saleprice(0.0), discount(0.0) {}
//    Sales_data(std::istream& is)
//    {
    
    
//        is >> *this;
//    }

public:
    Sales_data& combine(const Sales_data& rhs)
    {
    
    
        units_sold += rhs.units_sold;
        saleprice = (rhs.saleprice * rhs.units_sold + saleprice * units_sold) / (rhs.units_sold + units_sold);
        sellingprice = (rhs.sellingprice * rhs.units_sold + sellingprice * units_sold) / (rhs.units_sold + units_sold);
        if (sellingprice != 0)
        {
    
    
            discount = saleprice / sellingprice;
        }
        return *this;
    }

    string isbn() const//只读不写
    {
    
    
        return bookNo;
    }

private:
    string bookNo;
    int units_sold = 0;
    double sellingprice = 0.0;
    double saleprice = 0.0;
    double discount = 0.0;

};

inline bool compareIsbn(const Sales_data& lhs, const Sales_data& rhs)
{
    
    
    return lhs.isbn() == rhs.isbn();
}

Sales_data add(const Sales_data& lhs, const Sales_data& rhs)
{
    
    
    Sales_data sum = lhs;
    sum.combine(rhs);
    return sum;
}
istream& read(istream& is, Sales_data& item)
{
    
    
    is >> item.bookNo >> item.units_sold >> item.sellingprice >> item.saleprice;
    return is;
}
ostream& print(ostream& os, const Sales_data& item)
{
    
    
    os << item.isbn() << " " << item.units_sold << " " << item.sellingprice << " " << item.saleprice << " " << item.discount;
    return os;
}

main.cpp

#include<iostream>
using namespace std;
#include"Sales_data.h"


int main()
{
    
    
	Sales_data total;
	Sales_data trans;

	cout << "请输入：（ISBN，销售量，原价，实际售价）" << endl;

	if (read(cin,total))
	{
    
    
		while (read(cin, trans))
		{
    
    
			if (compareIsbn(total, trans))
			{
    
    
				total = add(total, trans);
			}
			else
			{
    
    
				cout << "ISBN ，销售量， 原价，平均销售价格，折扣:";
				print(cout, total);
				cout << endl;
				total = trans;
			}
		}
		cout << "ISBN ，销售量， 原价，平均销售价格，折扣:";
		print(cout, total);
		cout << endl;
	}
	else
	{
    
    
		cout << "无数据" << endl;
	}


	system("pause");
	return 0;
}

7.8

#include<iostream>
using namespace std;
#include<cstring>

class Person
{
    
    
	friend istream& read(istream& is, Person& per);
	friend 	ostream& print(ostream& os, const Person& per);

public:
	string getname()const
	{
    
    
		return name;
	}
	string getaddress()const
	{
    
    
		return address;
	}

private:
	string name;
	string address;
};

istream& read(istream& is, Person& per)
{
    
    
	is >> per.name >> per.address;
	return is;
}

ostream& print(ostream& os, const Person& per)
{
    
    
	os << per.getname() << per.getaddress() << endl;
	return os;
}

int main()
{
    
    

	system("pause");
	return 0;
}

7.11

第三个构造函数为什么const std::string &s 要使用引用，其他不加？

对不容易确定大小但又不想传入之后被修改的对象，比如：vector、string等数据，一般加上const引用，用引用传参的方式避免不必要的拷贝构造导致的内存和cpu支出，cosnt的限定也保证了传入的参数不会被修改。对于int、double等简单类型，则一般使用传形参的方式，因为其大小较小而且确定，所以为了方便和保护传入的参数不被修改，一般都直接采用传形参

http://blog.csdn.net/cqk0100/article/details/72897504

Sales_data.h

#pragma once

#include<iostream>
#include<string>

class Sales_data
{
    
    
    friend istream& read(istream& is, Sales_data& item);
    friend ostream& print(ostream& os, const Sales_data& item);


public:
    Sales_data() = default;
    Sales_data(const string& s) :bookNo(s) {
    
    };
    Sales_data(const string& s, const int num, const double sell, double sale) :bookNo(s), units_sold(num), sellingprice(sell), saleprice(sale), discount(sale/sell) {
    
    };
    Sales_data(istream& is)
    {
    
    
        read(is, *this);
    }
public:
    Sales_data& combine(const Sales_data& rhs)
    {
    
    
        units_sold += rhs.units_sold;
        saleprice = (rhs.saleprice * rhs.units_sold + saleprice * units_sold) / (rhs.units_sold + units_sold);
        sellingprice = (rhs.sellingprice * rhs.units_sold + sellingprice * units_sold) / (rhs.units_sold + units_sold);
        if (sellingprice != 0)
        {
    
    
            discount = saleprice / sellingprice;
        }
        return *this;
    }

    string isbn() const//只读不写
    {
    
    
        return bookNo;
    }

private:
    string bookNo;
    int units_sold = 0;
    double sellingprice = 0.0;
    double saleprice = 0.0;
    double discount = 0.0;

};

inline bool compareIsbn(const Sales_data& lhs, const Sales_data& rhs)
{
    
    
    return lhs.isbn() == rhs.isbn();
}

Sales_data add(const Sales_data& lhs, const Sales_data& rhs)
{
    
    
    Sales_data sum = lhs;
    sum.combine(rhs);
    return sum;
}
istream& read(istream& is, Sales_data& item)
{
    
    
    is >> item.bookNo >> item.units_sold >> item.sellingprice >> item.saleprice;
    return is;
}
ostream& print(ostream& os, const Sales_data& item)
{
    
    
    os << item.isbn() << " " << item.units_sold << " " << item.sellingprice << " " << item.saleprice << " " << item.discount;
    return os;
}

main.cpp

#include<iostream>
using namespace std;
#include"Sales_data.h"


void test1()
{
    
    
	Sales_data item1;
	print(cout, item1);
	cout << endl;

	Sales_data item2("xxxxxxxx");
	print(cout, item2);
	cout << endl;

	Sales_data item3("xxxxxxxx", 2, 3, 4);
	print(cout, item3);
	cout << endl;

	Sales_data item4(cin);
	print(cout, item4);
	cout << endl;
}

int main()
{
    
    
	test1();

	system("pause");
	return 0;
}

7.12

同上，上面没有定义在外部

7.13

Sales_data.h

同上

main.cpp

#include<iostream>
using namespace std;
#include"Sales_data.h"


int main()
{
    
    
	Sales_data total(cin);
	Sales_data trans;

	cout << "请输入：（ISBN，销售量，原价，实际售价）" << endl;

	if (cin)
	{
    
    
		while (read(cin,trans))
		{
    
    
			if (compareIsbn(total, trans))
			{
    
    
				total.combine(trans);
			}
			else
			{
    
    
				cout << "ISBN ，销售量， 原价，平均销售价格，折扣" << total << endl;
				total = trans;
			}
		}
		cout << "ISBN ，销售量， 原价，平均销售价格,折扣" << total << endl;
	}
	else
	{
    
    
		cout << "无数据" << endl;
	}


	system("pause");
	return 0;
}

7.14

就用普通的构造方式一样

7.15

#include<iostream>
using namespace std;
#include<cstring>

class Person
{
    
    
public:
	Person(const string& n, const string& ad) :name(n), address(ad) {
    
    }
public:
	string getname()const
	{
    
    
		return name;
	}
	string getaddress()const
	{
    
    
		return address;
	}

private:
	string name;
	string address;
};

int main()
{
    
    

	system("pause");
	return 0;
}

7.26

1.内部声明+外部inline显式内联

2.直接内部定义，隐式内联

7.27

#include <iostream>
#include <string>
using namespace std;

class Screen
{
    
    
public:
	typedef string::size_type pos;

	Screen() = default;

	Screen(pos wd, pos he)
	{
    
    
		width = wd;
		height = he;
	}

	Screen(pos wd, pos he, char c)
	{
    
    
		width = wd;
		height = he;
		contents.assign(wd * he, c);
	}

	Screen& set(char c)
	{
    
    
		contents[cursor] = c;
		return *this;
	}

	Screen& set(pos r, pos col, char c)
	{
    
    
		contents[r * width + col] = c;
		return *this;
	}

	Screen& move(pos r, pos col)
	{
    
    
		cursor = r * width + col;
		return *this;
	}

	Screen& display(ostream& os)
	{
    
    
		do_display(os);
		return *this;
	}

	const Screen& display(ostream& os)const
	{
    
    
		do_display(os);
		return *this;
	}

private:
	pos height = 0;
	pos width = 0;
	pos cursor = 0;
	string contents;//存放数据

	void do_display(ostream& os)const//p248页解释，是个建议，把他单独写出来
	{
    
    
		os << contents;
	}
};

int main()
{
    
    

	Screen myScreen(5, 5, 'x');
	myScreen.move(4, 0).set('#').display(cout);
	cout << endl;
	myScreen.display(cout);
	cout << endl;

	system("pause");
	return 0;
}

7.31

class Y;

class X
{
    
    
	Y* a;
};
class Y
{
    
    
	X* b;
};

7.32

class window_mgr
{
    
    
public:
	typedef vector<Screen>::size_type ScreenIndex;

	void clear(ScreenIndex i)
	{
    
    
		Screen& s = screens[i];
		s.contents.assign(s.height * s.width, ' ');
	}

private:
	vector<Screen>screens{
    
     Screen(24,80,' ') };

};

7.41

#pragma once

#include<iostream>
#include<string>

class Sales_data
{
    
    
    friend istream& read(istream& is, Sales_data& item);
    friend ostream& print(ostream& os, const Sales_data& item);


public:
    Sales_data(const string& s, const int num, const double sell, double sale) :bookNo(s), units_sold(num), sellingprice(sell), saleprice(sale), discount(sale / sell) {
    
     cout << "1" << endl; }
    Sales_data() :Sales_data(" ", 0, 0, 0) {
    
     cout << "2" << endl; }
    Sales_data(const string& s) :Sales_data(s, 0, 0, 0) {
    
     cout << "3" << endl; }
    
    Sales_data(istream& is):Sales_data()
    {
    
    
        read(is, *this);
        cout << "4" << endl;
    }
public:
    Sales_data& combine(const Sales_data& rhs)
    {
    
    
        units_sold += rhs.units_sold;
        saleprice = (rhs.saleprice * rhs.units_sold + saleprice * units_sold) / (rhs.units_sold + units_sold);
        sellingprice = (rhs.sellingprice * rhs.units_sold + sellingprice * units_sold) / (rhs.units_sold + units_sold);
        if (sellingprice != 0)
        {
    
    
            discount = saleprice / sellingprice;
        }
        return *this;
    }

    string isbn() const//只读不写
    {
    
    
        return bookNo;
    }
    
    double avg_price()const
    {
    
    
        if (units_sold)
        {
    
    
            return sellingprice / units_sold;
        }
        else
        {
    
    
            return 0;
        }
    }
private:
    string bookNo;
    int units_sold = 0;
    double sellingprice = 0.0;
    double saleprice = 0.0;
    double discount = 0.0;

};

inline bool compareIsbn(const Sales_data& lhs, const Sales_data& rhs)
{
    
    
    return lhs.isbn() == rhs.isbn();
}

Sales_data add(const Sales_data& lhs, const Sales_data& rhs)
{
    
    
    Sales_data sum = lhs;
    sum.combine(rhs);
    return sum;
}
istream& read(istream& is, Sales_data& item)
{
    
    
    is >> item.bookNo >> item.units_sold >> item.sellingprice >> item.saleprice;
    return is;
}
ostream& print(ostream& os, const Sales_data& item)
{
    
    
    os << item.isbn() << " " << item.units_sold << " " << item.sellingprice << " " << item.saleprice << " " << item.discount;
    return os;
}

#include<iostream>
using namespace std;
#include"Sales_data.h"


int main()
{
    
    
	Sales_data sd1("aaaaa", 11, 11, 11);
	Sales_data sd2;
	Sales_data sd3("aaa");
	Sales_data sd4(cin);

	system("pause");
	return 0;
}

7.53

#include <iostream>
using namespace std;

class Debug
{
    
    
public:
	constexpr Debug(bool b = 1) :hd(b), io(b), other(b){
    
     }
	constexpr Debug(bool a, bool b, bool c) : hd(a),io(b),other(c){
    
     }
	
	constexpr bool any() {
    
     return hd || io || other; }

	void set_hd(bool b) {
    
     hd = b; }
	void set_io(bool b) {
    
     io = b; }
	void set_other(bool b) {
    
     other = b; }

private:
	bool hd;
	bool io;
	bool other;
};

int main()
{
    
    

	system("pause");
	return 0;
}

[C++primer]第四章，第五章，第六章，第七章课后习题

文章目录

第四章

4.21

4.22

第五章

5.12

5.14

5.17

5.20

5.21

5.25

第六章

6.3

6.4

6.5

6.9

6.10

6.12

6.17

6.21

6.22

6.23

6.25

6.26

6.27

6.32

6.33

6.56

第七章

7.1

7.2

7.3

7.4 7.5

7.6

7.7

7.8

7.11

7.12

7.13

7.14

7.15

7.26

7.27

7.31

7.32

7.41

7.53

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