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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