字符串转换为整数

下面代码仅供本人复习所用，实用性N低，各位飘过吧~~哈哈:>

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//

// 字符串转换为整数.

//

 

#include <cstdlib>

#include <iostream>

#include <string>

 

long toInteger(const std::string &str)

{

    bool isNegative = false;

    long result = 0;

    size_t i;

    const size_t length = str.length();

     

    //

    // 跳过非数字或符号的字符.

    //

    for (i = 0; i < length && ('0' > str[i] || '9' < str[i]); ++i)

    {

        //

        // 处理负号.

        //

        if ('-' == str[i] && '0' <= str[i + 1] && '9' >= str[i + 1])

        {

            isNegative = true;

            i++;

            break;

        }

    }

 

    //

    // 处理数字.

    //

    while (i < length && '0' <= str[i] && '9' >= str[i])

    {

        result = 10 * result + (str[i++] - '0');

    }

     

    return true == isNegative ? result * -1 : result;

}

 

int main(void)

{

    std::cout << toInteger("123456") << std::endl;

    std::cout << toInteger("-123456") << std::endl;

    std::cout << toInteger("--123456-") << std::endl;

    std::cout << toInteger("abBsD-123456") << std::endl;

    std::cout << toInteger("abBsD-123456XddeE") << std::endl;

    std::cout << toInteger("abBsD123456XddeE") << std::endl;

    return EXIT_SUCCESS;

}