17.1 17.2
#include <iostream> #include<vector> #include<tuple> int main() { std::tuple<int, int, int> t1{ 10,20,30 }; std::tuple<std::string, std::vector<std::string>, std::pair<std::string, int>>t2{ "hello",{"1","2","3"},{"string",1} }; }17.3 原版程序设计更加正式，方便重构。而使用tuple更快捷，方便调试。 17.4
typedef tuple<vector<Sales_data>::size_type, vector<Sales_data>::const_iterator, vector<Sales_data>::const_iterator> matches; vector<matches> findBook(const vector<vector<Sales_data>>& files, const string& s) { vector<matches>ret; for (auto it=files.cbegin();it!=files.cend();++it) { auto found = equal_range(it->cbegin(), it->cend(), s,compareIsbn); if (found.first != found.second) ret.push_back({ it - files.cbegin(),found.first,found.second }); } return ret; }17.5
typedef pair<vector<Sales_data>::size_type, pair< vector<Sales_data>::const_iterator, vector<Sales_data>::const_iterator>> matches_pair; vector<matches_pair> findBook_pair(const vector<vector<Sales_data>>& files, const string& s) { vector<matches_pair>ret; for (auto it = files.cbegin(); it != files.cend(); ++it) { auto found = equal_range(it->cbegin(), it->cend(),s,compareIsbn); if (found.first != found.second) ret.push_back(make_pair( it - files.cbegin(),make_pair(found.first,found.second)) ); } return ret; }17.6
struct matches_struct { matches_struct(vector<Sales_data>::size_type s, vector<Sales_data>::const_iterator b, vector<Sales_data>::const_iterator e) :sz(s), beg(b), end(e) {} vector<Sales_data>::size_type sz; vector<Sales_data>::const_iterator beg; vector<Sales_data>::const_iterator end; }; vector<matches_struct> findBook_struct(const vector<vector<Sales_data>>& files, const string& s) { vector<matches_struct>ret; for (auto it = files.cbegin(); it != files.cend(); ++it) { auto found = equal_range(it->cbegin(), it->cend(), s, compareIsbn); if (found.first != found.second) ret.push_back(matches_struct(it - files.cbegin(),found.first,found.second)); } return ret; }17.7 tuple版本更好，更加灵活。 17.8 将会默认初始化一个对象 17.9
000000000000000000000000000000000000000000000000000000000010000000000000000011110110100110110101取决于你输入的字符串17.10
#include <iostream> #include<vector> #include<bitset> int main() { std::vector<int>ivec{ 1,2,3,5,8,13,21 }; std::bitset<32>bits1; for (auto i : ivec) bits1.set(i); std::bitset<32>bits2; for (unsigned int i = 0; i < 32; i++) { bits2[i] = bits1[i]; } }17.11 17.12 17.13
#include <iostream> #include<bitset> template<unsigned N> struct Quiz { template<std::size_t M> friend std::ostream& operator<<(std::ostream& os,const Quiz<M>&); Quiz() = default; Quiz(const std::string& s) :bitquiz(s) {} void update(std::pair<unsigned, bool>); int grade(const Quiz& correct); private: std::bitset<N>bitquiz; }; template<unsigned N> void Quiz<N>::update(std::pair<unsigned, bool>p) { bitquiz.set(p.first, p.second); } template<unsigned N> int Quiz<N>::grade(const Quiz& correct) { auto grade = bitquiz ^ correct.bitquiz; grade.flip(); return grade.count(); } template<std::size_t M> std::ostream& operator<<(std::ostream& os, const Quiz<M>&q) { os << q.bitquiz << std::endl; return os; } int main() { std::string s1("1111100000"); Quiz<10> q1(s1); q1.update({ 0, 1 }); std::cout << q1 << std::endl; std::cout << q1.grade(Quiz<10>(std::string("1111100001"))) << std::endl; }17.14
try { regex r("[[:alnum:]+\\.(cpp|cxx|cc)$", regex::icase); } catch (regex_error e) { cout << e.what() << " code: " << e.code() << endl; } try { regex r1("[[:anum:]]+\\.(cpp|cxx|cc)$", regex::icase); } catch (std::regex_error e) { cout << e.what() << "code: " << e.code() << endl; }17.15
regex r("[[:alpha:]]*[^c]ei[[:alpha:]]*", regex::icase); string s; cout << "Please input a word! Input 'q' to quit!" << endl; std::smatch results; while (cin >> s && s != "q") { if (std::regex_match(s,results, r)) cout << "Input word " << results.str() << " is error!" << endl; else cout << "Input word " << s << " is okay!" << endl; cout << "Please input a word! Input 'q' to quit!" << endl; }17.16 只有[^c]ei初始化，只能匹配到字符串长度为3的非c开头的字符串ei 17.17 17.18
#include <iostream> #include<regex> #include<vector> using namespace std; int main() { regex pattern("[[:alpha:]]*[^c]ei[[:alpha:]]*",regex::icase); string s; cout << "Please input a sequence of words:" << endl; getline(cin, s); cout << endl; vector<string>svec{ "albeit","neighbor" }; for (sregex_iterator it(s.cbegin(), s.cend(), pattern), end_it; it != end_it; it++) { if (find(svec.cbegin(), svec.cend(), it->str()) != svec.end()) continue; cout << it->str() << " "; } }17.19 因为空字符串也可以比较 17.20
#include <iostream> #include <regex> using namespace std; bool vaild(const smatch& m) { if (m[1].matched) return m[3].matched && (m[4].matched == false || m[4].str() == " "); else return !m[3].matched && m[4].str() == m[6].str(); } int main() { string phone = "(\\()?(\\d{3})(\\))?([-. ])?(\\d{3})([-. ])?(\\d{4})"; regex r(phone); string s; smatch m; while (getline(cin, s)) { for (sregex_iterator it(s.cbegin(), s.cend(), r), end_it; it != end_it; it++) { if (vaild(*it)) cout << "Valid: " << it->str() << endl; else cout << "Not vaild: " << it->str() << endl; } } }17.21
#include <iostream> #include<fstream> #include <regex> #include<vector> #include<sstream> using namespace std; struct PersonInfo { string name; vector<string>phones; }; bool read_record(istream& is, vector<PersonInfo>& people) { if (is) { string line, phone; while (getline(is, line)) { PersonInfo info; istringstream record(line); record >> info.name; while (record >> phone) { info.phones.push_back(phone); } people.push_back(info); } return true; } else return false; } bool valid(const smatch& m) { if (m[1].matched) return m[3].matched && (m[4].matched == false || m[4].str() == " "); else return !m[3].matched && m[4].str() == m[6].str(); } int main() { string phone = "(\\()?(\\d{3})(\\))?([-. ])?(\\d{3})([-. ])?(\\d{4})"; regex r(phone); vector<PersonInfo>people; ifstream ifs("C:\\Users\\Kaji\\Desktop\\PeopleInfo.txt"); if (read_record(ifs, people))//读取文件中的信息，传入到vector中 { smatch result; for (auto person : people)//两层循环，对每个人的所有电话号码甄别，并分别输出错误与正确的电话号码 { ostringstream formatted, badNums; for (auto it=person.phones.begin();it!=person.phones.end();it++) { if (regex_match(*it, result, r) && valid(result)) formatted << *it << " "; else badNums << *it << " "; } if (!formatted.str().empty()) cout << person.name << " " << formatted.str() << endl; if (!badNums.str().empty()) cout << person.name << " invalid number(s) " << badNums.str() << endl; } } }17.22
“(\()?(\d{3})(\))?([[:blank:]])?(\d{3})([[:blank:]])?(\d{4})”
17.23
#include <iostream> using std::cin; using std::cout; using std::endl; using std::string; #include <regex> using std::regex; using std::smatch; using std::sregex_iterator; bool valid(const std::smatch& m) { if (m[2].matched && !m[3].matched) return false; else return true; } int main() { string code = "(\\d{5})([-])?(\\d{4})?"; regex r(code); string line; smatch m; while (cin>>line) { if(std::regex_search(line,m,r)) { if (valid(m)) cout << "Valid postal code: " << m.str() << endl; else cout << "Invalid postal code: " << m.str() << endl; } } return 0; }17.24
#include <iostream> #include <regex> #include <string> using namespace std; int main() { string pattern = "(\\()?(\\d{3})(\\))?([-. ])?(\\d{3})([-. ])?(\\d{4})"; string format = "$2.$5.$7"; regex r(pattern); string s; while (getline(cin, s)) { cout << regex_replace(s, r, format) << endl; } return 0; }17.25
#include <iostream> #include <regex> #include <string> using namespace std; int main() { string pattern = "(\\()?(\\d{3})(\\))?([-. ])?(\\d{3})([-. ])?(\\d{4})"; string fmt = "$2.$5.$7."; regex r(pattern); string s; while (getline(cin, s)) { smatch result; regex_search(s, result, r); if (!result.empty()) { cout << result.format(fmt) << endl; } else { cout << "No match" << endl; } } return 0; }17.26
#include <iostream> #include <regex> #include <string> using namespace std; int main() { string pattern = "(\\()?(\\d{3})(\\))?([-. ])?(\\d{3})([-. ])?(\\d{4})"; string fmt = "$2.$5.$7."; regex r(pattern); string s; smatch result; while (getline(cin, s)) { sregex_iterator test(s.cbegin(), s.cend(),r),end_it; if (test == end_it) { cout << "No match" << endl; } else if (++test != end_it) { sregex_iterator it(s.cbegin(), s.cend(), r); it++; for (; it != end_it; it++) { cout << it->format(fmt) << " "; } } else { for (sregex_iterator it(s.cbegin(), s.cend(), r); it != end_it; it++) { cout << it->format(fmt) << " "; } } cout << endl; } return 0; }17.27
#include <iostream> using std::cin; using std::cout; using std::endl; using std::string; #include <regex> using std::regex; using std::smatch; using std::sregex_iterator; bool valid(const smatch& m) { if (m[2].matched && !m[3].matched) return false; else return true; } int main() { string code = "(\\d{5})([-. ])?(\\d{4})?"; regex r(code); string line; smatch m; string fmt = "$1-$3"; while (cin>>line) { if (std::regex_search(line, m, r)) { if (valid(m)&& m[3].matched) cout << "Valid postal code: " << m.format(fmt) << endl; else if(valid(m)) cout << "Valid postal code: " << m.str()<< endl; else cout << "Invalid postal code: " << m.str() << endl; } else cout << "NO match " << endl; } return 0; }17.31 每次循环都会产生同样的值 17.32 未定义的标识符 17.33 来源
include <iostream> using std::cout; using std::endl; #include <fstream> using std::ifstream; #include <string> using std::string; #include <vector> using std::vector; #include <random> using std::default_random_engine; using std::uniform_int_distribution; #include <ctime> using std::time; #include <algorithm> using std::sort; using std::find_if; #include <utility> using std::pair; int main() { typedef pair<string, string> ps; ifstream i("d.txt"); vector<ps> dict; string str1, str2; // read wirds from dictionary while (i >> str1 >> str2) { dict.emplace_back(str1, str2); } i.close(); // sort words in vector sort(dict.begin(), dict.end(), [](const ps &_ps1, const ps &_ps2){ return _ps1.first < _ps2.first; }); i.open("i.txt"); default_random_engine e(unsigned int(time(0))); // read words from text while (i >> str1) { // find word in dictionary vector<ps>::const_iterator it = find_if(dict.cbegin(), dict.cend(), [&str1](const ps &_ps){ return _ps.first == str1; }); // if word doesn't exist in dictionary if (it == dict.cend()) { // write it itself cout << str1 << ' '; } else { // get random meaning of word uniform_int_distribution<unsigned> u (0, find_if(dict.cbegin(), dict.cend(), [&str1](const ps &_ps){ return _ps.first > str1; }) - it - 1); // write random meaning cout << (it + u(e))->second << ' '; } } return 0; }17.34 略 17.35
#include <iostream> using namespace std; int main() { cout <<uppercase<< "defalut format: "<<hexfloat << 100 * sqrt(2.0) << endl; cout << "scientific: : " << scientific << 100 * sqrt(2.0) << endl; }17.36
int main() { cout <<"default format: " << 100 * sqrt(2.0) << '\n' << "scientific: " << scientific << 100 * sqrt(2.0) << '\n' << "fixed decimal: " << fixed << 100 * sqrt(2.0) << '\n' << "hexidecimal: " << uppercase << hexfloat << 100 * sqrt(2.0) << '\n' << "use defaults: " << defaultfloat << 100 * sqrt(2.0) << "\n\n"; }17.37
int main() { cout <<left<<setw(15) << "default format:" <<setw(25)<< right<< 100 * sqrt(2.0) << '\n' << left << setw(15) << "scientific:" << scientific << setw(25) << right << 100 * sqrt(2.0) << '\n' << left << setw(15) << "fixed decimal:" << setw(25) << fixed << right << 100 * sqrt(2.0) << '\n' << left << setw(15) << "hexidecimal:" << setw(25) << uppercase << hexfloat << right << 100 * sqrt(2.0) << '\n' << left << setw(15) << "use defaults:" << setw(25) << defaultfloat << right << 100 * sqrt(2.0) << "\n\n"; }17.37 空行不影响输入，长度超过字符数组大小的行会损坏堆栈
#include <iostream> #include<fstream> using namespace std; int main() { char a[40]; ifstream ifs("C:\\Users\\Kaji\\Desktop\\test.txt"); while (ifs) { ifs.getline(a, 40); cout << a << endl; } }17.38
#include <iostream> #include<fstream> using namespace std; int main() { char a[40]; ifstream ifs("C:\\Users\\Kaji\\Desktop\\test.txt"); while (ifs) { ifs.getline(a, 40); int size = ifs.gcount(); cout.write(a, size); cout << endl; } }17.39
#include <iostream> #include<fstream> #include<string> using namespace std; int main() { fstream file("C:\\Users\\Kaji\\Desktop\\test.txt", fstream::in | fstream::out | fstream::ate); auto end_mark = file.tellg(); file.seekg(0,fstream::beg); string line; size_t size = 0; while (file && file.tellg() != end_mark&&getline(file,line)) { size += line.size()+1; auto mark = file.tellg(); file.seekg(0,fstream::end); file << size; if (mark != end_mark) file << " "; file.seekg(mark); } file.seekg(0,fstream::end); file << '\n'; file.seekg(0,fstream::beg); while (getline(file, line)) { cout << line << endl; } return 0; }