[LeetCode]Roman to Integer

題目說明:

Given a roman numeral, convert it to an integer.

Input is guaranteed to be within the range from 1 to 3999.

 

程序代碼:

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

    //{'I','V','X','L','C','D','M','#','#'};
    //  1   5  10  50  100 500 1000

int getSingleRomanInt(char s)
{
    int nResult = 0;
    switch (s)
    {
    case 'I':
        nResult = 1;
        break;
    case 'V':
        nResult = 5;
        break;
    case 'X':
        nResult = 10;
        break;
    case 'L':
        nResult = 50;
        break;
    case 'C':
        nResult = 100;
        break;
    case 'D':
        nResult = 500;
        break;
    case 'M':
        nResult = 1000;
        break;
    }

    return nResult;
}

int romanToInt1(string s) 
{
    int nResult = 0;
    int nLength = s.length();
    if (nLength == 0)
    {
        return 0;
    }

    int nPre = getSingleRomanInt(s[0]);
    int nTemp = nPre;
    for (int i = 1; i < nLength; ++i)
    {
        int nCurrent = getSingleRomanInt(s[i]);
        if (nPre == nCurrent)
        {
            nTemp += nCurrent;
        }
        else if(nPre < nCurrent)
        {
            nTemp = nCurrent - nTemp;
        }
        else
        {
            nResult += nTemp;
            nTemp = nCurrent;
        }

        nPre = nCurrent;
    }

    nResult += nTemp;
    return nResult;
}

// 雖然羅馬數字的書寫規則較爲複雜，但根據羅馬數字「左加右減」的規律，
// 能夠構造出更簡單的羅馬數字轉換阿拉伯數字的方法：即從右向左（從低位向高位）考察羅馬數字，
// 遇到比上一個數字大的數字就加上，遇到比上一個數字小的數字就減去。
int romanToInt(string s) 
{
    int nResult = 0;
    int nLength = s.length();
    if (nLength == 0)
    {
        return 0;
    }

    int nPre = 0;
    for (int i = nLength-1; i >=0; i--)
    {
        int nCurrent = getSingleRomanInt(s[i]);
        if (nCurrent < nPre)
        {
            nResult -= nCurrent;
            nPre = nCurrent;
        }
        else
        {
            nResult += nCurrent;
            nPre = nCurrent;
        }
    }

    return nResult;
}

TEST(Pratices, tRomanToInt)
{
    // DLLXXXVII => 687
    ASSERT_EQ(romanToInt("DCLXXXVII"),687);

    // CCI => 201
    ASSERT_EQ(romanToInt("CCI"),201);

    // MMMCMXCIX => 3999
    ASSERT_EQ(romanToInt("MMMCMXCIX"),3999);

    // CDLVI => 456
    ASSERT_EQ(romanToInt("CDLVI"),456);

    // XCIX => 99
    ASSERT_EQ(romanToInt("XCIX"),99);

    ASSERT_EQ(romanToInt("IV"),4);
}

參考相關:

http://articles.leetcode.com/palindrome-number