c++中的std_c++ stoi

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1. 函数原型

int stoi (const string&  str, size_t* idx = 0, int base = 10);
int stoi (const wstring& str, size_t* idx = 0, int base = 10);

2. 参数说明

• str

String object with the representation of an integral number.

• idx

Pointer to an object of type size_t, whose value is set by the function to position of the next character in 
str after the numerical value.

This parameter can also be a null pointer, in which case it is not used.

• base

Numerical base (radix) that determines the valid characters and their interpretation.

If this is 
0, the base used is determined by the format in the sequence (see strtol for details). Notice that by default this argument is 
10, not 
0.

3. 返回值

如果解析成功，返回转换后的整数。

On success, the function returns the converted integral number as an int value.

4. 异常处理

stoi当字符串不符合规范时，会抛出异常，所以在使用stoi时应该有必要的异常处理：

#include <stdexcept>
#include <iostream>
#include <string>
using namespace std;
 
int main()
{
    std::string y = "253647586946334221002101219955219971002";
    int x;
 
    try {
        x = stoi(y);
    }
    catch (std::invalid_argument&){
        // If no conversion could be performed, an invalid_argument exception is thrown.
        cout << "Invalid_argument" << endl;
    }
    catch (std::out_of_range&){
        // If the value read is out of the range of representable values by an int, an out_of_range exception is thrown.
        cout << "Out of range" << endl;
    }
    catch (...) {
        // everything else
        cout << "Something else" << endl;
    }
    return 0;
}

参考资料：

• https://blog.csdn.net/u014694994/article/details/79074566
• http://www.cplusplus.com/reference/string/stoi/?kw=stoi

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