详解C++中stoi/stol/stoll函数的用法

stoi()函数

#include <string>
int stoi(const std::string& str, std::size_t* pos = 0, int base = 10);
int stoi(const std::wstring& str, std::size_t* pos = 0, int base = 10);

功能:将字符串str转成 有符号 int 整数

参数:

  • str:字符串
  • pos:存储将字符串str转成有符号整数,处理了str中字符的个数的地址,默认为NULL
  • base:进制,10:十进制,8:八进制,16:十六进制,0:则自动检测数值进制,str是 0 开头为八进制,str是 0x 或 0X 开头是十六进制,默认为十进制

stoi()函数指定转换字符串为十进制用法

#include <iostream>
#include <string>
using namespace std;
 
int main(int argc, char *argv[])
{
 int a;
 size_t pos = 0;
 string str;
 
 str = "-1235";
 a = stoi(str);
 cout << "a = " << a << endl; //a = -1235
 
 str = "1235";
 a = stoi(str);
 cout << "a = " << a << endl; //a = 1235
 
 str = " -12 35"; 
 a = stoi(str, &pos); //会舍弃空白符
 cout << "a = " << a << endl; //a = -12
 cout << "pos = " << pos << endl; //pos = 5
 
 str = " -12ab35";
 a = stoi(str, &pos);
 cout << "a = " << a << endl; //a = -12
 cout << "pos = " << pos << endl; //pos = 5
 
 str = "0123";
 a = stoi(str);
 cout << "a = " << a << endl; //a = 123
 
 str = "0x123";
 a = stoi(str);
 cout << "a = " << a << endl; //a = 0
 
 return 0;
}

stoi()函数指定转换字符串为十六进制用法

#include <iostream>
#include <string>
using namespace std;
 
int main(int argc, char *argv[])
{
 int a;
 size_t pos = 0;
 string str;
 
 str = "0x123";
 a = stoi(str, NULL, 16); //base = 16,指定十六进制
 cout << "a = " << a << endl; //a = 291
 
 str = "0x123";
 a = stoi(str, NULL, 0); //base = 0,自动检测数值进制
 cout << "a = " << a << endl; //a = 291
 
 str = "-12";
 a = stoi(str, &pos, 16); //-(2 + 1*16)
 cout << "a = " << a << endl; //a = -18
 cout << "pos = " << pos << endl; //pos = 3
 
 str = "12";
 a = stoi(str, &pos, 16); //2 + 1*16
 cout << "a = " << a << endl; //a = 18
 cout << "pos = " << pos << endl; //pos = 2
 
 str = " -12 35"; 
 a = stoi(str, &pos, 16); //会舍弃空白符
 cout << "a = " << a << endl; //a = -18
 cout << "pos = " << pos << endl; //pos = 5
 
 str = " -ab";
 a = stoi(str, &pos, 16); //-(11 + 10*16)
 cout << "a = " << a << endl; //a = -171
 cout << "pos = " << pos << endl; //pos = 5
 
 str = "0123";
 a = stoi(str, NULL, 16); //(3 + 2*16 + 1*16*16)
 cout << "a = " << a << endl; //a = 291
 
 return 0;
}

stoi()函数指定转换字符串为八进制用法

#include <iostream>
#include <string>
using namespace std;
 
int main(int argc, char *argv[])
{
 int a;
 size_t pos = 0;
 string str;
 
 str = "0x123";
 a = stoi(str, NULL, 8); //base = 8,指定八进制
 cout << "a = " << a << endl; //a = 0
 
 str = "0123"; //(3 + 2*8 + 1*8*8)
 a = stoi(str, NULL, 0); //base = 0,自动检测数值进制
 cout << "a = " << a << endl; //a = 83
 
 str = "-12";
 a = stoi(str, &pos, 8); //-(2 + 1*8)
 cout << "a = " << a << endl; //a = -10
 cout << "pos = " << pos << endl; //pos = 3
 
 str = "12";
 a = stoi(str, &pos, 8); //2 + 1*8
 cout << "a = " << a << endl; //a = 10
 cout << "pos = " << pos << endl; //pos = 2
 
 str = " -12 35"; 
 a = stoi(str, &pos, 8); //会舍弃空白符
 cout << "a = " << a << endl; //a = -10
 cout << "pos = " << pos << endl; //pos = 5
 
 // str = " -a78"; 
 // a = stoi(str, &pos, 8); //数字前有字母,调用会崩掉
 // cout << "a = " << a << endl; 
 // cout << "pos = " << pos << endl; 
 
 return 0;
}

stol()函数

#include <string>
long stol(const std::string& str, std::size_t* pos = 0, int base = 10);
long stol(const std::wstring& str, std::size_t* pos = 0, int base = 10);

功能:将字符串str转成 有符号 long 整数

参数:

  • str:字符串
  • pos:存储将字符串str转成有符号整数,处理了str中字符的个数的地址,默认为NULL
  • base:进制,10:十进制,8:八进制,16:十六进制,0:则自动检测数值进制,str是 0 开头为八进制,str是 0x 或 0X 开头是十六进制,默认为十进制

stol()函数指定转换字符串为十进制用法

#include <iostream>
#include <string>
using namespace std;
 
int main(int argc, char *argv[])
{
 long a;
 size_t pos = 0;
 string str;
 
 str = "-1235";
 a = stol(str);
 cout << "a = " << a << endl; //a = -1235
 
 str = "1235";
 a = stol(str);
 cout << "a = " << a << endl; //a = 1235
 
 str = " -12 35"; 
 a = stol(str, &pos); //会舍弃空白符
 cout << "a = " << a << endl; //a = -12
 cout << "pos = " << pos << endl; //pos = 5
 
 str = " -12ab35";
 a = stol(str, &pos);
 cout << "a = " << a << endl; //a = -12
 cout << "pos = " << pos << endl; //pos = 5
 
 str = "0123";
 a = stol(str);
 cout << "a = " << a << endl; //a = 123
 
 str = "0x123";
 a = stol(str);
 cout << "a = " << a << endl; //a = 0
 
 return 0;
}

stol()函数指定转换字符串为十六进制用法

#include <iostream>
#include <string>
using namespace std;
 
int main(int argc, char *argv[])
{
 long a;
 size_t pos = 0;
 string str;
 
 str = "0x123";
 a = stol(str, NULL, 16); //base = 16,指定十六进制
 cout << "a = " << a << endl; //a = 291
 
 str = "0x123";
 a = stol(str, NULL, 0); //base = 0,自动检测数值进制
 cout << "a = " << a << endl; //a = 291
 
 str = "-12";
 a = stol(str, &pos, 16); //-(2 + 1*16)
 cout << "a = " << a << endl; //a = -18
 cout << "pos = " << pos << endl; //pos = 3
 
 str = "12";
 a = stol(str, &pos, 16); //2 + 1*16
 cout << "a = " << a << endl; //a = 18
 cout << "pos = " << pos << endl; //pos = 2
 
 str = " -12 35"; 
 a = stol(str, &pos, 16); //会舍弃空白符
 cout << "a = " << a << endl; //a = -18
 cout << "pos = " << pos << endl; //pos = 5
 
 str = " -ab";
 a = stol(str, &pos, 16); //-(11 + 10*16)
 cout << "a = " << a << endl; //a = -171
 cout << "pos = " << pos << endl; //pos = 5
 
 str = "0123";
 a = stol(str, NULL, 16); //(3 + 2*16 + 1*16*16)
 cout << "a = " << a << endl; //a = 291
 
 return 0;
}

stol()函数指定转换字符串为八进制用法

#include <iostream>
#include <string>
using namespace std;
 
int main(int argc, char *argv[])
{
 long a;
 size_t pos = 0;
 string str;
 
 str = "0x123";
 a = stol(str, NULL, 8); //base = 8,指定八进制
 cout << "a = " << a << endl; //a = 0
 
 str = "0123"; //(3 + 2*8 + 1*8*8)
 a = stol(str, NULL, 0); //base = 0,自动检测数值进制
 cout << "a = " << a << endl; //a = 83
 
 str = "-12";
 a = stol(str, &pos, 8); //-(2 + 1*8)
 cout << "a = " << a << endl; //a = -10
 cout << "pos = " << pos << endl; //pos = 3
 
 str = "12";
 a = stol(str, &pos, 8); //2 + 1*8
 cout << "a = " << a << endl; //a = 10
 cout << "pos = " << pos << endl; //pos = 2
 
 str = " -12 35"; 
 a = stol(str, &pos, 8); //会舍弃空白符
 cout << "a = " << a << endl; //a = -10
 cout << "pos = " << pos << endl; //pos = 5
 
 // str = " -a78"; 
 // a = stol(str, &pos, 8); //数字前有字母,调用会崩掉
 // cout << "a = " << a << endl; 
 // cout << "pos = " << pos << endl; 
 
 return 0;
}

stoll()函数

#include <string>
long long stoll(const std::string& str, std::size_t* pos = 0, int base = 10);
long long stoll(const std::wstring& str, std::size_t* pos = 0, int base = 10);

功能:将字符串str转成 有符号 long long 整数

参数:

  • str:字符串
  • pos:存储将字符串str转成有符号整数,处理了str中字符的个数的地址,默认为NULL
  • base:进制,10:十进制,8:八进制,16:十六进制,0:则自动检测数值进制,str是 0 开头为八进制,str是 0x 或 0X 开头是十六进制,默认为十进制

stoll()函数指定转换字符串为十进制用法

#include <iostream>
#include <string>
using namespace std;
 
int main(int argc, char *argv[])
{
 long long a;
 size_t pos = 0;
 string str;
 
 str = "-1235";
 a = stoll(str);
 cout << "a = " << a << endl; //a = -1235
 
 str = "1235";
 a = stoll(str);
 cout << "a = " << a << endl; //a = 1235
 
 str = " -12 35"; 
 a = stoll(str, &pos); //会舍弃空白符
 cout << "a = " << a << endl; //a = -12
 cout << "pos = " << pos << endl; //pos = 5
 
 str = " -12ab35";
 a = stoll(str, &pos);
 cout << "a = " << a << endl; //a = -12
 cout << "pos = " << pos << endl; //pos = 5
 
 str = "0123";
 a = stoll(str);
 cout << "a = " << a << endl; //a = 123
 
 str = "0x123";
 a = stoll(str);
 cout << "a = " << a << endl; //a = 0
 
 return 0;
}

stoll()函数指定转换字符串为十六进制用法

#include <iostream>
#include <string>
using namespace std;
 
int main(int argc, char *argv[])
{
 long long a;
 size_t pos = 0;
 string str;
 
 str = "0x123";
 a = stoll(str, NULL, 16); //base = 16,指定十六进制
 cout << "a = " << a << endl; //a = 291
 
 str = "0x123";
 a = stoll(str, NULL, 0); //base = 0,自动检测数值进制
 cout << "a = " << a << endl; //a = 291
 
 str = "-12";
 a = stoll(str, &pos, 16); //-(2 + 1*16)
 cout << "a = " << a << endl; //a = -18
 cout << "pos = " << pos << endl; //pos = 3
 
 str = "12";
 a = stoll(str, &pos, 16); //2 + 1*16
 cout << "a = " << a << endl; //a = 18
 cout << "pos = " << pos << endl; //pos = 2
 
 str = " -12 35"; 
 a = stoll(str, &pos, 16); //会舍弃空白符
 cout << "a = " << a << endl; //a = -18
 cout << "pos = " << pos << endl; //pos = 5
 
 str = " -ab";
 a = stoll(str, &pos, 16); //-(11 + 10*16)
 cout << "a = " << a << endl; //a = -171
 cout << "pos = " << pos << endl; //pos = 5
 
 str = "0123";
 a = stoll(str, NULL, 16); //(3 + 2*16 + 1*16*16)
 cout << "a = " << a << endl; //a = 291
 
 return 0;
}

stoll()函数指定转换字符串为八进制用法

#include <iostream>
#include <string>
using namespace std;
 
int main(int argc, char *argv[])
{
 long long a;
 size_t pos = 0;
 string str;
 
 str = "0x123";
 a = stoll(str, NULL, 8); //base = 8,指定八进制
 cout << "a = " << a << endl; //a = 0
 
 str = "0123"; //(3 + 2*8 + 1*8*8)
 a = stoll(str, NULL, 0); //base = 0,自动检测数值进制
 cout << "a = " << a << endl; //a = 83
 
 str = "-12";
 a = stoll(str, &pos, 8); //-(2 + 1*8)
 cout << "a = " << a << endl; //a = -10
 cout << "pos = " << pos << endl; //pos = 3
 
 str = "12";
 a = stoll(str, &pos, 8); //2 + 1*8
 cout << "a = " << a << endl; //a = 10
 cout << "pos = " << pos << endl; //pos = 2
 
 str = " -12 35"; 
 a = stoll(str, &pos, 8); //会舍弃空白符
 cout << "a = " << a << endl; //a = -10
 cout << "pos = " << pos << endl; //pos = 5
 
 // str = " -a78"; 
 // a = stoll(str, &pos, 8); //数字前有字母,调用会崩掉
 // cout << "a = " << a << endl; 
 // cout << "pos = " << pos << endl; 
 
 return 0;
}

注意:stoi、stol、stoll 函数是C++11标准加入的,用g++编译器编译需要加参数:-std=c++11

作者:微尘8原文地址:https://blog.csdn.net/d704791892/article/details/129706412

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