c++のメモ
概要
c++についての自分用のメモ書き
g++
g++ がサポートしている規格
$ g++ --version g++ (Ubuntu 4.8.4-2ubuntu1~14.04.3) 4.8.4 Copyright (C) 2013 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. $ g++ -v --help 2>/dev/null | grep -E "^\s+\-std=.*$" -std=<standard> Assume that the input sources are for <standard> -std=f2003 Conform to the ISO Fortran 2003 standard -std=f2008 Conform to the ISO Fortran 2008 standard -std=f2008ts Conform to the ISO Fortran 2008 standard -std=f95 Conform to the ISO Fortran 95 standard -std=gnu Conform to nothing in particular -std=legacy Accept extensions to support legacy code -std=c++03 Conform to the ISO 1998 C++ standard revised by -std=c++0x Deprecated in favor of -std=c++11 -std=c++11 Conform to the ISO 2011 C++ standard -std=c++1y Conform to the ISO 201y(7?) C++ draft standard -std=c++98 Conform to the ISO 1998 C++ standard revised by -std=c11 Conform to the ISO 2011 C standard (experimental -std=c1x Deprecated in favor of -std=c11 -std=c89 Conform to the ISO 1990 C standard -std=c90 Conform to the ISO 1990 C standard -std=c99 Conform to the ISO 1999 C standard -std=c9x Deprecated in favor of -std=c99 -std=gnu++03 Conform to the ISO 1998 C++ standard revised by -std=gnu++0x Deprecated in favor of -std=gnu++11 -std=gnu++11 Conform to the ISO 2011 C++ standard with GNU -std=gnu++1y Conform to the ISO 201y(7?) C++ draft standard -std=gnu++98 Conform to the ISO 1998 C++ standard revised by -std=gnu11 Conform to the ISO 2011 C standard with GNU -std=gnu1x Deprecated in favor of -std=gnu11 -std=gnu89 Conform to the ISO 1990 C standard with GNU -std=gnu90 Conform to the ISO 1990 C standard with GNU -std=gnu99 Conform to the ISO 1999 C standard with GNU -std=gnu9x Deprecated in favor of -std=gnu99 -std=iso9899:1990 Conform to the ISO 1990 C standard -std=iso9899:199409 Conform to the ISO 1990 C standard as amended in -std=iso9899:1999 Conform to the ISO 1999 C standard -std=iso9899:199x Deprecated in favor of -std=iso9899:1999 -std=iso9899:2011 Conform to the ISO 2011 C standard (experimental
引数
引数を２倍して出力する
参考 - C++で文字列を数値に変換する方法 - C++と色々 - http://www7b.biglobe.ne.jp/~robe/cpphtml/html03/cpp03042.html
https://github.com/ludwig125/work/blob/master/src/cpp/test/argv.cpp
#include <iostream> #include <stdlib.h> using namespace std; int main(int argc, char** argv) { for(int i = 1; i < argc; i++){ cout << "argv "<< i << " : " << argv[i] << endl; cout << "double argv: " << atoi(argv[i])*2 << endl; } return 0; }
実行結果
$ g++ argv.cpp [~/git/work/src/cpp/test ] $ ./a.out 13 83 argv 1 : 13 double argv: 26 argv 2 : 83 double argv: 166
型変換
- 変数の型変換
型を確認
#include <iostream> #include <stdlib.h> #include <typeinfo> using namespace std; int main(int argc, char** argv) { int a,b; for(int i = 1; i < argc; i++){ cout << "argv "<< i << " : " << argv[i] << endl; } // 引数の型 cout << typeid(argv[1]).name() << " : " << argv[1] << endl; a = atoi(argv[1]); b = atoi(argv[2]); // 変換後の型 cout << typeid(a).name() << " : " << a << endl; return 0; }
実行結果
$ ./a.out 10 30 argv 1 : 10 argv 2 : 30 Pc : 10 i : 10
typeidの出力
Uses of typeid in C++ - Codeforces
bool = b char = c unsigned char = h short = s unsigned short = t int = i unsigned int = j long = l unsigned long = m long long = x unsigned long long = y float = f double = d long double = e string = Ss int[] = A_i double[] = A_d vector<int> = St6vectorIiSaIiE
c++のstringへの変換について
to_stringが使えない
あまり考えずにto_stringを使おうとしたら、以下のコンパイルエラーが出た
error: ‘to_string’ is not a member of ‘std’
c++11にするとか、コンパイル時の指定が必要とか書いてある c++ - "to_string" isn't a member of "std"? - Stack Overflow
面倒なので他の方法を探してみる
stringstreamを使う
stringstreamを使った方法が見つかった
参考 - [O] C++ で int 型の値を string 型にするときは stringstream - 文字列⇔数値 - code snippets - C++11で数字→文字列はstd::to_string()、文字列→数字はstd::stoi()とかstd::stod()とか - minus9d's diary
やってみる
超適当なコード
$ cat stringToint.cpp #include <iostream> #include <string> #include <sstream> int main(void) { int a = 3; float b = 3.14; double c = 2.99792458; std::string d= "this is test"; std::string str; std::stringstream ss; ss << a; str = ss.str(); std::cout << str << std::endl; ss.str(""); ss << b; str = ss.str(); std::cout << str << std::endl; ss.str(""); ss << c; str = ss.str(); std::cout << str << std::endl; ss.str(""); ss << d; str = ss.str(); std::cout << str << std::endl; }
実行結果
$ g++ stringToint.cpp $ ./a.out 3 3.14 2.99792 this is test
vector
vectorのソート
参考： - http://blog.sarabande.jp/post/62062199465 - http://kaworu.jpn.org/cpp/std::sort
https://github.com/ludwig125/work/blob/master/src/cpp/test/sort_vector.cpp
#include <iostream> #include <algorithm> #include <vector> using namespace std; int main() { vector<int> v; v.push_back ( 3 ); v.push_back ( 4 ); v.push_back ( 1 ); v.push_back ( 2 ); std::sort(v.begin(), v.end(), std::greater<int>() ); for(vector<int>::iterator it = v.begin(); it != v.end(); it++){ cout << *it << endl; } return 0; }
実行結果
[~/git/work/src/cpp/test ] $ ./a.out 4 3 2 1 [~/git/work/src/cpp/test ] $
文字列を受け取って１文字ずつvectorに格納
#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main()
{
string str;
getline(cin,str);
string tmp;
// 'abcde'のような文字列を一文字ずつvectorに格納
vector<string> v;
for(int i = 0; i < (int)str.size(); i++){
char ch = str[i];
cout << ch << " " << endl;
// v.push_back(string(ch));
// 直接charをvectorに格納しようとしたらコンパイルエラーになったのでstringの変数に入れた
tmp = ch;
v.push_back(tmp);
}
cout << "output vector" << endl;
for(vector<string>::iterator it = v.begin(); it != v.end(); it++){
cout << *it << endl;
}
return 0;
}
