这是《C++ primer》中的一个示例程序，看了几遍仍觉有些细节没有明白，故手敲了一遍

需了解STL容器部分知识点，智能指针，文件流，string流

《C++ primer》文本查询程序一

书上给的例子尚有瑕疵，如果单词在同一行出现多次，则只会记录为一次，本人能力有限，尚未解决此问题

以下是写完程序后绘制的思维导图

代码部分

• main.cpp

#include<iostream>
#include<fstream>
#include"TextQuery.h"
#include"ResultQuery.h"
using namespace std;

void runQueries(ifstream& fin);

int main(void)
{
    string filename;
    cout << "请输入你要查询的文件名(包含后缀)"<<endl;
    cin >> filename;
	ifstream readFile(filename, ios::in);
	if (readFile.is_open())
	{
		runQueries(readFile);
	}
	else
		cout << "the file open failed!!!" << endl;
}

void runQueries(ifstream& fin)
{
	TextQuery tq(fin);
	while (1)
	{
		cout << "please enter word to look for, or q to quit." << endl;
		string needle;
		if (cin >> needle && needle != "q" && needle != "Q")
		{
			MyPrint(cout, tq.query(needle)) << endl;
		}
		else break;
	}
}

• TextQuery.h

#pragma once
#include<memory>
#include<string>
#include<map>
#include<set>
#include<vector>
#include"ResultQuery.h"

using namespace std;

class TextQuery {
private:
	shared_ptr<vector<string>> file;   //智能指针 多个对象共享数据 存储地址
	map<string, shared_ptr<set<int>>> wm; //间接实现单词与行号之间的映射
public:
	TextQuery(ifstream& fin);   //构造函数
	ResultQuery query(string needle); //用来整理出目标单词的相关信息，然后传递给ResultQuery
};

• TextQuery.cpp

#include "TextQuery.h"
#include<string>
#include<sstream>
#include<fstream>
using namespace std;
TextQuery::TextQuery(ifstream& fin):file(new vector<string>)
{
	string lineContent;
	size_t lineNo;
	while(getline(fin,lineContent))    // 将文件内容拆分为一行一行
	{
		file->push_back(lineContent);
		lineNo = file->size() - 1;    //从零开始计数，方便之后利用迭代器进行输出查询结果
		istringstream line(lineContent); //利用string流 将一行内容再拆分为每个单词
		string word;
		while (line >> word)     //实现每个单词与对应行号之间的映射
		{
			shared_ptr<set<int>>& NO = wm[word];  // 在map中如果使用下标未找到对应的值，则会自动生成一个默认值
			if (!NO)
			{
				NO.reset(new set<int>);    //清空默认值，使其是一个指向set<int>型的指针
				NO->insert(lineNo);        //将这个单词所在的行号拷贝给 指针指向的那个空间
			}
			else
				NO->insert(lineNo);
		}
	}
}

ResultQuery TextQuery::query(string needle)
{
	shared_ptr<set<int>> nothing (new set<int>);
	auto result = wm.find(needle);
	if (result == wm.end())
	{
		return ResultQuery(needle,file, nothing);
	}
	else
	{
		return ResultQuery(needle,file, result->second);
	}
}

• ResultQuery.h

#pragma once
#include<memory>
#include<string>
#include<vector>
#include<set>
#include<map>
using namespace std;
class ResultQuery
{
private:
	string needle;
	shared_ptr<vector<string>> file;
	shared_ptr<set<int>> lines;
public:
	ResultQuery(string n, shared_ptr<vector<string>> f, shared_ptr<set<int>> l) :\
		needle(n), file(f), lines(l) {}    //构造函数 进行初始化
	friend ostream& MyPrint(ostream&, const ResultQuery&);
};

• ResultQuery.cpp

#include "ResultQuery.h"
#include <iostream>
ostream& MyPrint(ostream& os, const ResultQuery& rq) {
	os<< rq.needle << " occurs " << rq.lines->size() << "times in the file "  << endl;
	for (auto line : *(rq.lines))
	{
		os << "\tline:"<<line+1<< " "<<rq.file->begin()[line]<<endl;
	}
	return os;
}