c++ primer 学习笔记-第十二章

习题12.2：

头文件：

#ifndef STRBLOB_H#define STRBLOB_H#include <vector>  #include <string> #include <memory>#include <initializer_list>#include <stdexcept>class StrBlob{public:using size_type = std::vector<std::string>::size_type;StrBlob();StrBlob(std::initializer_list<std::string> s);size_type size()const{ return data->size(); }bool empty()const{ return data->empty(); }//添加&删除元素void push_back(const std::string &t){ data->push_back(t); }void pop_back();//需要检查还是否有元素，若为空则抛出异常//元素访问std::string &front();std::string &back();const std::string &front()const;//overload versionconst std::string &back()const;private://github上学的，成员函数与数据成员分开void check(size_type i, const std::string &msg)const;//包括异常处理private:std::shared_ptr<std::vector<std::string>> data;};//类外定义构造函数StrBlob::StrBlob() :data(std::make_shared<std::vector<std::string>>()){ };StrBlob::StrBlob(std::initializer_list<std::string> s) :data(std::make_shared<std::vector<std::string>>(s)){ };void StrBlob::check(size_type i, const std::string &msg)const{if (i >= data->size())throw std::out_of_range(msg);}std::string &StrBlob::front(){check(0, "front on empty StrBlob");return data->front();}const std::string &StrBlob::front()const{check(0, "front on empty StrBlob");return data->front();}std::string &StrBlob::back(){check(0, "back on empty StrBlob");return data->back();}const std::string &StrBlob::back()const{check(0, "back on empty StrBlob");return data->back();}void StrBlob::pop_back(){check(0, "pop_back on empty StrBlob");data->pop_back();}#endif

习题12.6：

#include <iostream>  #include <fstream>  #include <vector>  #include <string>  #include <map>  #include <set>  #include <algorithm>  #include <utility>  #include "StrBlob.h"using std::cin; using std::cout; using std::endl;using std::vector; using std::string;using std::istream; using std::ifstream;using std::map; using std::set; using std::pair;vector<int> *ret(){return new vector<int>;}vector<int> *read(vector<int> *pv){int i = 0;while (cin >> i)pv->push_back(i);return pv;}void print(vector<int> *pv){for (auto i : *pv)cout << i << " ";cout << endl;}int main(){auto pv = ret();read(pv);print(pv);delete pv;getchar();return 0;}

习题12.7：

#include <iostream>  #include <fstream>  #include <vector>  #include <string>  #include <map>  #include <set>  #include <algorithm>  #include <utility>  #include <memory>#include "StrBlob.h"using std::cin; using std::cout; using std::endl;using std::vector; using std::string;using std::istream; using std::ifstream;using std::map; using std::set; using std::pair;using Ptr = std::shared_ptr<vector<int>>;auto ret()->Ptr{return std::make_shared<vector<int>>();}auto read(Ptr pv)->Ptr{int i = 0;while (cin >> i)pv->push_back(i);return pv;}void print(Ptr pv){for (auto i : *pv)cout << i << " ";cout << endl;}int main(){print(read(ret()));getchar();return 0;}

习题12.20：

int main(){ifstream infile("有标点单词段落测试.txt");StrBlob str;for (string s; std::getline(infile, s); str.push_back(s));StrBlobPtr str_ptr(str);for (auto i = 0; i != str.size() && cout << str_ptr.deref() << endl; str_ptr.incr())++i;getchar();return 0;}

习题12.26：

#include <iostream>  #include <fstream>  #include <vector>  #include <string>  #include <map>  #include <set>  #include <algorithm>  #include <utility>  #include <memory>using std::cin; using std::cout; using std::endl;using std::vector; using std::string;using std::istream; using std::ifstream;using std::map; using std::set; using std::pair;using std::allocator;int main(){std::size_t n = 7;allocator<string> alloc;auto const p = alloc.allocate(n);auto q = p;string s;while (cin >> s && q != p + n)alloc.construct(q++, s);//use of itwhile (q != p){cout << *--q << endl;alloc.destroy(q);}alloc.deallocate(p,n);getchar();return 0;}

习题12.30：

Query.h

#ifndef QUERY_H#define QUERY_H#include <vector>#include <string>#include <iostream>#include <fstream>#include <sstream>#include <algorithm>#include <memory>#include <map>#include <set>class QueryResult;class TextQuery{public:using line_no = std::vector<std::string>::size_type;TextQuery(std::ifstream &);QueryResult query(const std::string &)const;private:std::shared_ptr<std::vector<std::string>> file;std::map<std::string, std::shared_ptr<std::set<line_no>>> wm;};class QueryResult{friend std::ostream &print(std::ostream &is, const QueryResult &qr);public:using line_no = std::vector<std::string>::size_type;QueryResult(std::string s,std::shared_ptr<std::set<line_no>> l, std::shared_ptr<std::vector<std::string>> f):sought(s), lines(l), file(f){ };private:std::string sought;std::shared_ptr<std::set<line_no>> lines;std::shared_ptr<std::vector<std::string>> file;};#endif

Query.cpp

#include "Query.h"TextQuery::TextQuery(std::ifstream &ifs) :file(new std::vector<std::string>){for (std::string line_text; std::getline(ifs,line_text); line_text.clear()){                                  //外层循环处理行，内层处理单词及行数set//std::cout << line_text << std::endl;file->push_back(line_text);    //将该行内容压入容器int n = file->size() - 1;      //记录当前行号std::istringstream iss(line_text);for (std::string word_raw,word_new; iss >> word_raw; word_new.clear()){std::remove_copy_if(word_raw.begin(), word_raw.end(), std::back_inserter(word_new), ispunct);auto &lines = wm[word_new];//获取指向set的shared_ptr，用引用可避免引用计数增加if (!lines)lines.reset(new std::set<line_no>);lines->insert(n);}}}QueryResult TextQuery::query(const std::string &sought)const{static std::shared_ptr<std::set<line_no>> nodata(new std::set<line_no>);auto loc = wm.find(sought);if (loc == wm.end())return QueryResult(sought, nodata, file);elsereturn QueryResult(sought, loc->second, file);}std::string make_plural(std::size_t n, const std::string &s1, const std::string &s2){return n <= 1 ? s1 : s1 + s2;}std::ostream &print(std::ostream &os, const QueryResult &qr){os << "element occurs " << qr.lines->size()<< make_plural(qr.lines->size(), "time", "s") << std::endl;for (auto l : *(qr.lines))os << "\t(line " << l + 1 << ") "<< *(qr.file->begin() + l) << std::endl;return os;}

main.cpp

#include "Query.h"void runQuery(std::ifstream &infile){TextQuery tq(infile);while (true){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(){std::ifstream infile("184.txt");runQuery(infile);getchar();return 0;}