1. AI技术聚合首页
  2. IT

C++stoi、stol、stoll 函数用法

乘风 • • IT • 阅读 28

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
int 整数

参数：

str：字符串

pos：存储将字符串 str 转成
int 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
long 整数

参数：

str：字符串

pos：存储将字符串str转成
long 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
long long 整数

参数：

str：字符串

pos：存储将字符串 str 转成
long long 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;
}

总结：

stoi 函数：将字符串转成 int 整数。

stol 函数：将字符串转成 long 整数。

stoll 函数：将字符串转成 long long 整数。

使用时需要注意的是 stoi、stol、stoll 函数是 C++11标准 加入的，用 g++ 编译器编译时需要加参数：-std=c++11

版权声明：本文为博主作者：微尘8原创文章，版权归属原作者，如果侵权，请联系我们删除！

原文链接：https://blog.csdn.net/d704791892/article/details/129706412

共计人评分，平均分

到目前为止还没有投票！成为第一位评论此文章。

赞 (0)
乘风的头像乘风管理团队
0
上一篇 2024年4月1日
下一篇 2024年4月1日

相关推荐