C++字符串轉化為int類型的利器stoi函數詳解

一、定義及參數介紹

1. int stoi (const string& str, size_t* idx = 0, int base = 10);
2. int stoi (const wstring& str, size_t* idx = 0, int base = 10);
3. 所屬頭文件為string.h
4. 參數：

• str:表示所要轉化的字符串
• idx:表示想要str中開始轉化的位置，默認為從第一個字符開始。
• base:表示要用的進制（如2進制、16進制，默認為10進制）轉化為int類型十進制數字。

二、例子

// stoi example
#include <iostream>   // std::cout
#include <string>     // std::string, std::stoi

int main ()
{
  std::string str_dec = "2001, A Space Odyssey";
  std::string str_hex = "40c3";
  std::string str_bin = "-10010110001";
  std::string str_auto = "0x7f";

  std::string::size_type sz;   // alias of size_t

  int i_dec = std::stoi (str_dec,&sz);
  int i_hex = std::stoi (str_hex,nullptr,16);
  int i_bin = std::stoi (str_bin,nullptr,2);
  int i_auto = std::stoi (str_auto,nullptr,0);

  std::cout << str_dec << ": " << i_dec << " and [" << str_dec.substr(sz) << "]\n";
  std::cout << str_hex << ": " << i_hex << '\n';
  std::cout << str_bin << ": " << i_bin << '\n';
  std::cout << str_auto << ": " << i_auto << '\n';

  return 0;
}

OUT:
2001, A Space Odyssey: 2001 and [, A Space Odyssey]
40c3:  16579
-10010110001: -1201
0x7f: 127