c++primer第五版第十二章练习

12.1

b1=b2，所以都有4个元素，赋值后b1原先指向的内存被释放，因为计数为0

b2离开作用域后被摧毁，但计数器不为0，内存不用释放

12.2

#ifndef HEAD_H_#define HEAD_H_#include <memory>#include <initializer_list>#include <string>#include <vector>class StrBlob{std::shared_ptr<std::vector<std::string>> data;void check(std::vector<std::string>::size_type i, const std::string &msg)const;public:using size_type = std::vector<std::string>::size_type;StrBlob();StrBlob(std::initializer_list<std::string> il);size_type size()const;//返回vector元素数量bool empty()const;//是否为空void push_back(const std::string &t);//添加新元素到尾void pop_back();//弹出最后一个std::string front()const;std::string back()const;std::string &front();//返回第一个std::string &back();//返回最后一个};void StrBlob::check(std::vector<std::string>::size_type i, const std::string &msg)const{if (i >= data->size())throw std::out_of_range(msg);}StrBlob::StrBlob() :data(std::make_shared<std::vector<std::string>>()){}StrBlob::StrBlob(std::initializer_list<std::string> il) : data(std::make_shared<std::vector<std::string>>(il)){}StrBlob::size_type StrBlob::size()const{return data->size();}bool StrBlob::empty()const{return data->empty();}void StrBlob::push_back(const std::string &t){data->push_back(t);}void StrBlob::pop_back(){check(0, "pop_push on empty StrBlob");data->pop_back();}std::string &StrBlob::front(){check(0, "front on empty StrBlob");return data->front();}std::string &StrBlob::back(){check(0, "back on empty StrBlob");return data->back();}std::string StrBlob::front()const{return data->front();}std::string StrBlob::back()const{return data->back();}#endif

#include <iostream>#include "标头.h"int main(){using namespace std;StrBlob strb{ "dsdsdsd", "dsdsdsdsd" ,"dasdafwafwadwa","fwqdswqdeqdwqed"};cout << strb.front();strb.pop_back();cout << endl << strb.front();strb.pop_back();cout << strb.front();system("puse");return 0;}

12.3

可以这样做，但是然并卵

在方法形参为const时才会使用const版本

12.4

因为size_type是无符号类型，如果小于0将会自动转换为大于0的数

所以当参数为负数时，i肯定会比size()大

12.5

使用容易，因为可以自动转换参数类型

调试难，出问题时就悲剧

12.6

#include <iostream>#include <vector>void input(std::vector<int> &vec){int i;while (std::cin >> i)vec.push_back(i);}void print(const std::vector<int> &vec){for (auto a : vec)std::cout << a << "\t";}std::vector<int> *func(){return new std::vector<int>;}int main(){using namespace std;auto p = func();input(*p);print(*p);delete p;system("pause");return 0;}

12.7

#include <iostream>#include <memory> //shared_ptr....智能指针#include <vector>void input(std::shared_ptr<std::vector<int>> vec){int i;while (std::cin >> i)vec->push_back(i);}void print(const std::shared_ptr<std::vector<int>> vec){for (auto a : *vec)std::cout << a << "\t";}std::shared_ptr<std::vector<int>> func(){//return std::make_shared<std::vector<int>>();//创建一个智能指针分配内存，返回地址return std::shared_ptr<std::vector<int>>(new std::vector<int>);//new创建一个vector并隐式转换为智能指针，返回给智能指针初始化}int main(){using namespace std;auto p = func();input(p);print(p);system("pause");return 0;}

12.8

内存地址丢失

12.9

r=q后r原先指向的内存丢失

r2=q2后r2原先保存的计数器变为0，释放内存

12.10

可以这样，没有错误，然并卵

12.11

发生错误，当函数结束时会把get()返回的地址调用delete释放，使得p变成悬空指针

12.12

a：ok

b：error，new分配内存后返回的是一个普通指针，无法赋值到shared_ptr对象

c：error，p是一个普通指针，同上

d：ok，但容易发生错误，比较糟的做法

12.13

运行时错误，在delete后sp智能指针所管理的内存已经被释放，而当智能指针作用域过后会再释放一次

12.14

#include <iostream>#include <memory>//shared_ptr#include <string>struct destination{std::string ip;int port;destination(std::string _ip, int _port) :ip(_ip), port(_port){}};struct connection{std::string ip;int port;connection(std::string _ip, int _port) :ip(_ip), port(_port){}};connection connect(destination *p){std::shared_ptr<connection> ptr(new connection(p->ip, p->port));std::cout << "use_count:" << ptr.use_count() << std::endl;return *ptr;}void disconnect(connection p){std::cout << "close " << p.ip << std::endl;//delete ....//...}void end_connection(connection *p){disconnect(*p);}void f(destination &d){connection c = connect(&d);std::shared_ptr<connection> p(&c, end_connection);}int main(){using namespace std;destination d("192.168.1.233", 2333);f(d);system("pause");return 0;}

12.15

#include <iostream>#include <memory>//shared_ptr#include <string>struct destination{std::string ip;int port;destination(std::string _ip, int _port) :ip(_ip), port(_port){}};struct connection{std::string ip;int port;connection(std::string _ip, int _port) :ip(_ip), port(_port){}};connection connect(destination *p){std::shared_ptr<connection> ptr(new connection(p->ip, p->port));std::cout << "use_count:" << ptr.use_count() << std::endl;return *ptr;}void disconnect(connection p){std::cout << "close " << p.ip << std::endl;//delete ....//...}//void end_connection(connection *p)//{//disconnect(*p);//}void f(destination &d){connection c = connect(&d);std::shared_ptr<connection> p(&c, [](connection *p){disconnect(*p); });}int main(){using namespace std;destination d("192.168.1.233", 2333);f(d);system("pause");return 0;}

12.16

#include <iostream>#include <memory>//shared_ptrint main(){using namespace std;unique_ptr<int> p(new int(0));unique_ptr<int> p1(p);//它是已删除的函数unique_ptr<int> p2;p2 = p;//它是已删除的函数system("pause");return 0;}

12.17

a： 错误，ix是局部变量b：错误，同a

c：√ d：错误，同a

e：√ f：错误，多次释放同一位置内存

12.18

release会释放内存，无法保证计数为0

12.19

#ifndef HEAD_H_#define HEAD_H_#include <memory>#include <initializer_list>#include <string>#include <vector>class StrBlobPtr;class StrBlob{friend class StrBlobPtr;std::shared_ptr<std::vector<std::string>> data;void check(std::vector<std::string>::size_type i, const std::string &msg)const;public:using size_type = std::vector<std::string>::size_type;StrBlob();StrBlob(std::initializer_list<std::string> il);size_type size()const;//返回vector元素数量bool empty()const;//是否为空void push_back(const std::string &t);//添加新元素到尾void pop_back();//弹出最后一个std::string front()const;std::string back()const;std::string &front();//返回第一个std::string &back();//返回最后一个StrBlobPtr begin();StrBlobPtr end();};class StrBlobPtr{std::shared_ptr<std::vector<std::string>> check(std::size_t, const std::string &)const;std::weak_ptr<std::vector<std::string>> wptr;std::size_t curr;public:StrBlobPtr() :curr(0){}StrBlobPtr(StrBlob &a, std::size_t sz = 0) :wptr(a.data), curr(sz){}std::string &deref()const;//解引用StrBlobPtr &incr();//++n;运算符};void StrBlob::check(std::vector<std::string>::size_type i, const std::string &msg)const{if (i >= data->size())throw std::out_of_range(msg);}StrBlob::StrBlob() :data(std::make_shared<std::vector<std::string>>()){}StrBlob::StrBlob(std::initializer_list<std::string> il) : data(std::make_shared<std::vector<std::string>>(il)){}StrBlob::size_type StrBlob::size()const{return data->size();}bool StrBlob::empty()const{return data->empty();}void StrBlob::push_back(const std::string &t){data->push_back(t);}void StrBlob::pop_back(){check(0, "pop_push on empty StrBlob");data->pop_back();}std::string &StrBlob::front(){check(0, "front on empty StrBlob");return data->front();}std::string &StrBlob::back(){check(0, "back on empty StrBlob");return data->back();}std::string StrBlob::front()const{return data->front();}std::string StrBlob::back()const{return data->back();}StrBlobPtr StrBlob::begin(){ return StrBlobPtr(*this); }StrBlobPtr StrBlob::end(){return StrBlobPtr(*this, data->size());}std::shared_ptr<std::vector<std::string>> StrBlobPtr::check(std::size_t i, const std::string &msg)const{auto ret = wptr.lock();//返回shared_ptrif (!ret)throw std::runtime_error("unbound StrBlobPtr");if (i >= ret->size())throw std::out_of_range(msg);return ret;}std::string &StrBlobPtr::deref()const{auto ret = check(curr, "dereference past end");return (*ret)[curr];}StrBlobPtr &StrBlobPtr::incr(){check(curr, "increment past end of StrBlobPtr");++curr;return *this;}#endif

12.20

#include "标头.h"#include <iostream>#include <fstream>bool iseq(const StrBlobPtr &s1, const StrBlobPtr &s2)//StrBlobPtr的友元函数：当两个引用 不相等 时返回真{if (s1.wptr.lock() == s2.wptr.lock())return !(s1.curr == s2.curr);return true;}int main(int argc, char **argv){using namespace std;ifstream ifile("F:\\11.txt");if (!ifile){cerr << "open file error!";exit(1);}StrBlob str;string temp;while (getline(ifile, temp)){str.push_back(temp);}for (auto beg = str.begin(), end = str.end(); iseq(beg, end); beg.incr()){cout << beg.deref() << endl;}return 0;}

12.21

一样，但前一个版本好理解

12.22

#ifndef HEAD_H_#define HEAD_H_#include <memory>#include <initializer_list>#include <string>#include <vector>class ConstStrBlobPtr;class StrBlob{friend class ConstStrBlobPtr;std::shared_ptr<std::vector<std::string>> data;void check(std::vector<std::string>::size_type i, const std::string &msg)const;public:using size_type = std::vector<std::string>::size_type;StrBlob();StrBlob(std::initializer_list<std::string> il);size_type size()const;//返回vector元素数量bool empty()const;//是否为空void push_back(const std::string &t);//添加新元素到尾void pop_back();//弹出最后一个std::string front()const;std::string back()const;const std::string &front();//返回第一个constconst std::string &back();//返回最后一个 constConstStrBlobPtr begin();//curr=0ConstStrBlobPtr end();//curr=data->size();};class ConstStrBlobPtr{std::shared_ptr<std::vector<std::string>> check(std::size_t, const std::string &)const;std::weak_ptr<std::vector<std::string>> wptr;std::size_t curr;public:ConstStrBlobPtr() :curr(0){}ConstStrBlobPtr(const StrBlob &a, std::size_t sz = 0) :wptr(a.data), curr(sz){}//constconst std::string &deref()const;//解引用constConstStrBlobPtr &incr();//++n;运算符friend bool iseq(const ConstStrBlobPtr &, const ConstStrBlobPtr &);};void StrBlob::check(std::vector<std::string>::size_type i, const std::string &msg)const{if (i >= data->size())throw std::out_of_range(msg);}StrBlob::StrBlob() :data(std::make_shared<std::vector<std::string>>()){}StrBlob::StrBlob(std::initializer_list<std::string> il) : data(std::make_shared<std::vector<std::string>>(il)){}StrBlob::size_type StrBlob::size()const{return data->size();}bool StrBlob::empty()const{return data->empty();}void StrBlob::push_back(const std::string &t){data->push_back(t);}void StrBlob::pop_back(){check(0, "pop_push on empty StrBlob");data->pop_back();}const std::string &StrBlob::front(){check(0, "front on empty StrBlob");return data->front();}const std::string &StrBlob::back(){check(0, "back on empty StrBlob");return data->back();}std::string StrBlob::front()const{return data->front();}std::string StrBlob::back()const{return data->back();}ConstStrBlobPtr StrBlob::begin(){return ConstStrBlobPtr(*this);}ConstStrBlobPtr StrBlob::end(){return ConstStrBlobPtr(*this, data->size());}std::shared_ptr<std::vector<std::string>> ConstStrBlobPtr::check(std::size_t i, const std::string &msg)const{auto ret = wptr.lock();//返回shared_ptrif (!ret)throw std::runtime_error("unbound StrBlobPtr");if (i >= ret->size())throw std::out_of_range(msg);return ret;}const std::string &ConstStrBlobPtr::deref()const{auto ret = check(curr, "dereference past end");return (*ret)[curr];}ConstStrBlobPtr &ConstStrBlobPtr::incr(){check(curr, "increment past end of StrBlobPtr");++curr;return *this;}#endif

12.23

#include <iostream>#include <string>int main(){using namespace std;char s1[] = "c++ ";char s2[] = "primer";char *p = new char[strlen(s1) + strlen(s2)+1]();//要注意初始化strcat(p, s1);strcat(p, s2);cout << p << endl;delete[] p;string str1{ "c++" }, str2{ "primer" };auto str = str1 + str2;cout << str;system("pause");return 0;}

12.24

#include <iostream>int main(){using namespace std;char *str = new char[10];cin.get(str, 10);//只读取10个字符cout << str << endl;delete[]str;system("pause");return 0;}

12.25

deete [] pa;

12.26

#include <iostream>#include <string>#include <memory>//allcator//#include <vector>int main(){using namespace std;allocator<string> alloc;auto const p = alloc.allocate(10);auto q = p;string temp;//vector<string> vec;//while (vec.size() < 10)//{//cin >> temp;//++q;//vec.push_back(temp);//}////把vec中的元素拷贝到p指向的内地址中//uninitialized_copy(vec.begin(), vec.end(), p);while (q - p < 10){cout << q - p + 1 << ":";cin >> temp;alloc.construct(q++, temp);//把temp传递给string的构造函数构造一个对象存放到q指向的位置然后++把q指向下一个}const size_t size = q - p;q = p;while (q != p + size)cout << *q++ << endl;while (q != p)alloc.destroy(--q);//删除q指向的地址的对象数据alloc.deallocate(p,10);//释放p开始的10个string的地址的内存system("pause");return 0;}

12.27

#ifndef HEAD_H_#define HEAD_H_#include <iostream>#include <string>#include <fstream>#include <sstream>//istringstream//#include <iterator>//find#include <vector>#include <map>#include <set>#include <memory>//shared_ptr#include <cctype>class QueryResult;class TextQuery{std::vector<std::string> str;//把文件每一行都保存到string中std::map<std::string, std::set<std::vector<std::string>::size_type>> line;//保存单词对应的行号相当于map<string,set<unsigned>> line;std::string isword(std::string s){s[0] = tolower(s[0]);if (!isalnum(s[s.size() - 1]))s = std::string(s.begin(), s.end() - 1);return s;}public:TextQuery(std::ifstream &in){if (!in){std::cerr << "open file error in class";exit(1);}std::string temp;while (std::getline(in, temp)){str.push_back(temp);std::istringstream instr(temp);std::string t;while (instr >> t)line[isword(t)].insert(str.size()-1);}}QueryResult query(const std::string &s);};class QueryResult{public:std::string word;std::map<std::vector<std::string>::size_type, std::string> mw;friend std::ostream &print(std::ostream &os, const QueryResult &qr);QueryResult(){}};QueryResult TextQuery::query(const std::string &s){QueryResult qr;if (line.find(s) == line.cend()){std::cout << "not word\n";return qr;}qr.word = s;for (auto &x : line[s])qr.mw[x] = str[x];return qr;}#endif

#include "标头.h"std::ostream &print(std::ostream &os, const QueryResult &qr){os << qr.word << " occurs " << qr.mw.size() << " times" << std::endl;for (auto &x : qr.mw)os << "(line " << x.first +1<< ") " << x.second << std::endl;return os;}void runQuerues(std::ifstream &in){TextQuery tq(in);while (1){std::cout << "enter word to look for,or q to quit: ";std::string s;if (!(std::cin >> s) || s == "q")break;print(std::cout, tq.query(s)) << std::endl;}}int main(int argc, char **argv){using namespace std;ifstream infile(argv[1]);runQuerues(infile);return 0;}

12.28

#include <iostream>#include <fstream>#include <sstream>//istringstream#include <vector>#include <string>#include <map>#include <set>#include <cctype>int main(int argc, char **argv){using namespace std;ifstream infile(argv[1]);if (!infile){cerr << "open file error";exit(1);}vector<string> vec;map<string, set<vector<string>::size_type>> mw;string temp,word;while (getline(infile, temp)){vec.push_back(temp);istringstream ist(temp);while (ist >> word){if (!isalpha(word[0]))continue;word[0] = tolower(word[0]);if (!isalnum(word[word.size() - 1]))word.erase(word.size() - 1, 1);mw[word].insert(vec.size()-1);}}cout << "enter find word:";while (cin >> word){if (mw.find(word) == mw.cend()){cout << "not word!" << endl;continue;}cout << word << " occurs " << mw.size()<< " times" << endl;for (auto x : mw[word])cout << "(line " << x +1 << ") " << vec[x] << endl;}//system("pause");return 0;}

12.29

#ifndef HEAD_H_#define HEAD_H_#include <iostream>#include <string>#include <fstream>#include <sstream>//istringstream//#include <iterator>//find#include <vector>#include <map>#include <set>#include <memory>//shared_ptr#include <cctype>class QueryResult;class TextQuery{std::vector<std::string> str;//把文件每一行都保存到string中std::map<std::string, std::set<std::vector<std::string>::size_type>> line;//保存单词对应的行号相当于map<string,set<unsigned>> line;std::string isword(std::string s){s[0] = tolower(s[0]);if (!isalnum(s[s.size() - 1]))s = std::string(s.begin(), s.end() - 1);return s;}public:TextQuery(std::ifstream &in){if (!in){std::cerr << "open file error in class";exit(1);}std::string temp;do {if (!std::getline(in, temp))<span style="white-space:pre"></span>//.................do whilebreak;str.push_back(temp);std::istringstream instr(temp);std::string t;while (instr >> t)line[isword(t)].insert(str.size() - 1);} while (1);}QueryResult query(const std::string &s);};class QueryResult{public:std::string word;std::map<std::vector<std::string>::size_type, std::string> mw;friend std::ostream &print(std::ostream &os, const QueryResult &qr);QueryResult(){}};QueryResult TextQuery::query(const std::string &s){QueryResult qr;if (line.find(s) == line.cend()){std::cout << "not word\n";return qr;}qr.word = s;for (auto &x : line[s])qr.mw[x] = str[x];return qr;}#endif

#include "标头.h"std::ostream &print(std::ostream &os, const QueryResult &qr){os << qr.word << " occurs " << qr.mw.size() << " times" << std::endl;for (auto &x : qr.mw)os << "(line " << x.first + 1 << ") " << x.second << std::endl;return os;}void runQuerues(std::ifstream &in){TextQuery tq(in);do{std::cout << "enter word to look for,or q to quit: ";std::string s;if (!(std::cin >> s) || s == "q")break;print(std::cout, tq.query(s)) << std::endl;} while (1);}int main(int argc, char **argv){using namespace std;ifstream infile(argv[1]);runQuerues(infile);return 0;}

比较倾向以前一个版本，易理解，好判断

12.30

#ifndef HEAD_H_#define HEAD_H_#include <iostream>#include <fstream>//ifstream#include <string>#include <vector>#include <sstream>//istringstream#include <map>#include <set>#include <memory>//shared_ptrclass QueryResult;using line_no = std::vector < std::string > ::size_type;class TextQuery{std::shared_ptr<std::vector<std::string>> file;//保存整个文件内容，按行分std::map<std::string, std::shared_ptr<std::set<line_no>>> wm;//每个单词对应行号public:TextQuery(std::ifstream &is);QueryResult query(const std::string &s)const;//返回QR，单词、行号set，还有关联到文件内容};class QueryResult{friend std::ostream &print(std::ostream &os, const QueryResult &qr);std::string sought;std::shared_ptr<std::set<line_no>> lines;//记录出现的行号std::shared_ptr<std::vector<std::string>> file;//关联到文件内容public:QueryResult(std::string s, std::shared_ptr<std::set<line_no>> p, std::shared_ptr<std::vector<std::string>> f) :sought(s), lines(p), file(f){}};TextQuery::TextQuery(std::ifstream &is) :file(new std::vector<std::string>())//为智能指针file分配空间{std::string text;while (getline(is, text)){file->push_back(text);int n = file->size() - 1;std::istringstream line(text);std::string word;while (line >> word){auto &lines = wm[word];//如果word在wm中第一次出现，那么对应的set就未分配内存，所以为空if (!lines)//如果第一次出现lines.reset(new std::set<line_no>());lines->insert(n);}}}QueryResult TextQuery::query(const std::string &s)const{static std::shared_ptr<std::set<line_no>> nodata(new std::set<line_no>());//当没找到单词时返回内存常驻auto loc = wm.find(s);if (loc == wm.end())return QueryResult(s, nodata, file);elsereturn QueryResult(s, loc->second, file);}std::ostream &print(std::ostream &os, const QueryResult &qr){os << qr.sought << " occurs " << qr.lines->size() << " " << (qr.lines->size() > 1 ? "times" : "time") << std::endl;for (auto x : *qr.lines)//*(qr.file->begin()+x)os << "\t(line " << x + 1 << ") " << (*qr.file)[x] << std::endl;//file返回一个指向vec的智能指针，解引用后得到vector 然后使用下标运算符return os;}#endif

#include "标头.h"void runQueries(std::ifstream &infile){TextQuery tq(infile);while (1){std::cout << "enter word to look for, or q to quit:";std::string s;if (!(std::cin >> s) || s == "q")break;print(std::cout, tq.query(s));}}int main(int argc, char **argv){using namespace std;ifstream infile(argv[1]);if (!infile){cerr << "open file error!";exit(1);}runQueries(infile);return 0;}

12.31

使用insert时将出现重复行号，必须花费额外的代码处理

12.32

#ifndef HEAD1_H_#define HEAD1_H_#include <memory>#include <initializer_list>#include <string>#include <vector>class StrBlob{std::shared_ptr<std::vector<std::string>> data;void check(std::vector<std::string>::size_type i, const std::string &msg)const;public:using size_type = std::vector<std::string>::size_type;StrBlob();StrBlob(std::initializer_list<std::string> il);size_type size()const;//返回vector元素数量bool empty()const;//是否为空void push_back(const std::string &t);//添加新元素到尾void pop_back();//弹出最后一个std::string front()const;std::string back()const;std::string &front();//返回第一个std::string &back();//返回最后一个const std::shared_ptr<std::vector<std::string>> &shared_ptr()const//返回data的const引用{return data;}};void StrBlob::check(std::vector<std::string>::size_type i, const std::string &msg)const{if (i >= data->size())throw std::out_of_range(msg);}StrBlob::StrBlob() :data(std::make_shared<std::vector<std::string>>()){}StrBlob::StrBlob(std::initializer_list<std::string> il) : data(std::make_shared<std::vector<std::string>>(il)){}StrBlob::size_type StrBlob::size()const{return data->size();}bool StrBlob::empty()const{return data->empty();}void StrBlob::push_back(const std::string &t){data->push_back(t);}void StrBlob::pop_back(){check(0, "pop_push on empty StrBlob");data->pop_back();}std::string &StrBlob::front(){check(0, "front on empty StrBlob");return data->front();}std::string &StrBlob::back(){check(0, "back on empty StrBlob");return data->back();}std::string StrBlob::front()const{return data->front();}std::string StrBlob::back()const{return data->back();}#endif

#ifndef HEAD_H_#define HEAD_H_#include "标头1.h"#include <iostream>#include <fstream>//ifstream#include <string>#include <vector>#include <sstream>//istringstream#include <map>#include <set>#include <memory>//shared_ptrclass QueryResult;class TextQuery{std::shared_ptr<StrBlob> file;//保存整个文件内容，按行分std::map<std::string, std::shared_ptr<std::set<StrBlob::size_type>>> wm;//每个单词对应行号public:TextQuery(std::ifstream &is);QueryResult query(const std::string &s)const;//返回QR，单词、行号set，还有关联到文件内容};class QueryResult{friend std::ostream &print(std::ostream &os, const QueryResult &qr);std::string sought;std::shared_ptr<std::set<StrBlob::size_type>> lines;//记录出现的行号std::shared_ptr<StrBlob> file;//关联到文件内容public:QueryResult(std::string s,const std::shared_ptr<std::set<StrBlob::size_type>> &p, std::shared_ptr<StrBlob> f) :sought(s), lines(p), file(f){}};TextQuery::TextQuery(std::ifstream &is) :file(new StrBlob())//为智能指针file分配空间{std::string text;while (getline(is, text)){file->push_back(text);int n = file->size() - 1;std::istringstream line(text);std::string word;while (line >> word){auto &lines = wm[word];//如果word在wm中第一次出现，那么对应的set就未分配内存，所以为空if (!lines)//如果第一次出现lines.reset(new std::set<StrBlob::size_type>);lines->insert(n);}}}QueryResult TextQuery::query(const std::string &s)const{static std::shared_ptr<std::set<StrBlob::size_type>> nodata(new std::set<StrBlob::size_type>);//当没找到单词时返回内存常驻auto loc = wm.find(s);if (loc == wm.end())return QueryResult(s, nodata, file);elsereturn QueryResult(s, loc->second, file);}std::ostream &print(std::ostream &os, const QueryResult &qr){os << qr.sought << " occurs " << qr.lines->size() << " " << (qr.lines->size() > 1 ? "times" : "time") << std::endl;for (auto x : *qr.lines)os << "\t(line " << x + 1 << ") " << qr.file->shared_ptr()->at(x) << std::endl;//StrBlob需要添加返回data const引用的方法return os;}#endif

#include "标头.h"void runQueries(std::ifstream &infile){TextQuery tq(infile);while (1){std::cout << "enter word to look for, or q to quit:";std::string s;if (!(std::cin >> s) || s == "q")break;print(std::cout, tq.query(s));}}int main(int argc, char **argv){using namespace std;ifstream infile(argv[1]);if (!infile){cerr << "open file error!";exit(1);}runQueries(infile);return 0;}

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class QueryResult{friend std::ostream &print(std::ostream &os, const QueryResult &qr);std::string sought;std::shared_ptr<std::set<StrBlob::size_type>> lines;//记录出现的行号std::shared_ptr<StrBlob> file;//关联到文件内容public:QueryResult(std::string s,const std::shared_ptr<std::set<StrBlob::size_type>> &p, std::shared_ptr<StrBlob> f) :sought(s), lines(p), file(f){}std::set<StrBlob::size_type>::iterator begin()const{ return lines->begin(); }std::set<StrBlob::size_type>::iterator end()const{ return lines->end(); }std::shared_ptr<StrBlob> get_file()const{ return file; }};

2015年12月3日12:15:51