[算法练习] 把字符串转换成整数

#include <gtest/gtest.h>
using namespace std;

int StrToInt(const char* szValue, int nBase = 0, bool* bValid = NULL)
{    
    long long nValue = 0;
    int nSign = 1;
    
    if (bValid)
    {
        *bValid = false;
    }

    if (!szValue)
    {
        return 0;
    }

    if (nBase < 0 || nBase == 1 || nBase > 36)
    {
        return 0;
    }

    char cData = *szValue++;
    while(cData <= ‘ ‘)            // skip whitespace
    {
        cData = *szValue++;
    }

    if (cData == ‘+‘)
    {
        cData = *szValue++;
    }
    else if(cData == ‘-‘)
    {
        cData = *szValue++;
        nSign = -1;
    }

    if (nBase==0)
    {
        if (cData != ‘0‘)
            nBase = 10;
        else if (*szValue == ‘x‘ || *szValue == ‘X‘)
            nBase = 16;
        else
            nBase = 8;
    }

    if (nBase == 16)
    {
        if (cData == ‘0‘ && (*szValue == ‘x‘ || *szValue == ‘X‘))
        {
            szValue++;
            cData = *szValue++;
        }
    }

    while (cData != ‘\0‘)
    {
        int nData = 0;
        if (cData >= ‘0‘ && cData <= ‘9‘)
        {            
            nData = cData-‘0‘;
        }
        else if (cData >= ‘A‘ && cData <= ‘Z‘)
        {
            nData = cData - ‘A‘ + 10;
        }
        else if(cData >= ‘a‘ && cData <= ‘z‘)
        {
            nData = cData - ‘a‘ + 10;
        }
        else
        {
            break;
        }
        
        if (nData >= nBase) // bad digit
        {
            break;
        }

        nValue = (nBase * nValue) + nData;        
        if (nValue > std::numeric_limits<int>::max())
        {
            nValue = 0;
            break;
        }

        cData = *szValue++;
    }
        
    if (bValid)
    {
        *bValid = (cData == ‘\0‘);
    }
    
    return (int)(nSign * nValue);
}

TEST(Pratices, tStrToInt)
{    
    // NULL -> 0
    // ""  -> 0    
    // "0" -> 0
    // "+123" -> 123
    // "-123" -> -123
    // "123" -> 123
    
    ASSERT_EQ(StrToInt(NULL), 0);
    ASSERT_EQ(StrToInt(""), 0);
    ASSERT_EQ(StrToInt("0"), 0);
    ASSERT_EQ(StrToInt("+123"), 123);
    ASSERT_EQ(StrToInt("-123"), -123);
    ASSERT_EQ(StrToInt("123"), 123);

    // 16进制
    // 0x10 -> 16
    // 0x0 -> 0
    // 0x123 -> 291
    ASSERT_EQ(StrToInt("0x10"), 16);
    ASSERT_EQ(StrToInt("0x10",16), 16);
    ASSERT_EQ(StrToInt("0x0",16), 0);
    ASSERT_EQ(StrToInt("-0x123"), -291);
    
    // 8进制
    // 010 -> 8    
    // 0123 -> 83
    ASSERT_EQ(StrToInt("010"), 8);
    ASSERT_EQ(StrToInt("0123",8), 83);

}