C Primer Plus书中代码注释-chapter16_9.cpp

chapter16_9.cpp

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>

struct Review{
	std::string title;
	int rating;
}; 

bool operator<(const Review &r1, const Review  & r2);
bool worseThan(const Review & r1, const Review & r2);
bool FillReview(Review & rr);
void ShowReview(const Review & rr);

int main(){
	using namespace std;
	
	vector<Review> books;
	Review temp;
	while(FillReview(temp))			//当在review结构里插入了book，执行该循环 
		books.push_back(temp);
	if (books.size() > 0)			//只要插入了一本book，执行该循环，相对于前一个程序节省了一行代码，默认给size一个整型定义 
	{
		cout << "Thank you. You entered the following "
		<< books.size() << " ratings:\n" << "Rating\tBook\n";	//books是一个review结构的vector，每一个结构就是一个size 
		
		for_each(books.begin(), books.end(), ShowReview);		//遍历begin和end之间的元素，ShowReview隐式接收一个迭代器参数，
																//而且还对这个迭代器参数进行了解引用 
		
		sort(books.begin(), books.end());				//sort是对默认参数类型按照从小到大顺序排列的，对于新定义类型的排列，
														//这里给出了操作符operator<的排序规则，按照books的title成员的字母顺序升序排列
														//如果title的所有字母相同，则按照rating升序排列 
		cout << "Sorted by title:\nRating\tBook\n";
		for_each(books.begin(), books.end(), ShowReview);		//升序排列后展示 
		
		sort(books.begin(), books.end(), worseThan);		//按rating升序排列 
		cout << "Sorted by rating:\nRating\tBooks\n";
		for_each(books.begin(), books.end(), ShowReview);	//按rating升序排列后展示，这里函数的接口都是引用传入，传入的参数都是隐式的迭代器参数
		
		random_shuffle(books.begin(), books.end());			//随机排列 
		cout << "After shuffling:\nRating\tBook\n";
		for_each(books.begin(), books.end(), ShowReview);	//随机排列后展示 
	}
	else
		cout << "No entries. ";
	cout << "Bye.\n";
	
	return 0;
}

bool operator<(const Review & r1, const Review & r2)
{
	if (r1.title < r2.title)
		return true;
	else if (r1.title == r2.title && r1.rating < r2.rating)
		return true;
	else
		return false;
}

bool worseThan(const Review & r1, const Review & r2)
{
	if (r1.rating < r2.rating)
		return true;
	else
		return false;
}

bool FillReview(Review & rr)
{
	std::cout << "Enter book title (quit to quit): ";
	std::getline(std::cin, rr.title);
	if (rr.title == "quit")
		return false;
		std::cout << "Enter book rating: ";
		std::cin >> rr.rating;
		if(!std::cin)
			return false;
		while (std::cin.get() != '\n')
			continue;
		return true;
}

void ShowReview(const Review & rr)
{
	std::cout << rr.rating << "\t" << rr.title << std::endl;
}