C++ 整型与字符串的互转

C++ 整型与字符串的互转

flyfish

字符串转整型

C的方法 cstr是char*或者const char*类型的字符串
int num = atoi(str);
int num = strtol(cstr, NULL, 10);

//10 表示进制

C++11的方法

void test1(){   std::string str1 = "1";std::string str2 = "1.5";std::string str3 = "1 with words";int myint1 = std::stoi(str1);int myint2 = std::stoi(str2);int myint3 = std::stoi(str3);std::cout << "std::stoi(\"" << str1 << "\") is " << myint1 << '\n';std::cout << "std::stoi(\"" << str2 << "\") is " << myint2 << '\n';std::cout << "std::stoi(\"" << str3 << "\") is " << myint3 << '\n';}

结果输出
std::stoi(“1”) is 1
std::stoi(“1.5”) is 1
std::stoi(“1 with words”) is 1

//源码参考cplusplus.com

void test2(){  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;}

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

其他类型 类似
无符号整型
stoul

浮点型
stof

数值转字符串
std::string s;
s = std::to_string(1) + ” is int, “;

其他数值类型 类似
s = std::to_string(3.14f) + ” is float.”;