[LeetCode]Integer to Roman

题目说明:

Given an integer, convert it to a roman numeral.

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

程序代码:

思路是把数字拆成单独的部分，最后拼接起来

1. 拆分数字，求出每一位数字。

2. 把每位数字单独转换singleDigitToRoman成罗马数字，存入罗马数字数组strSingleResult[i]中

3. 最后拼接起来

 

单独转换方法singleDigitToRoman(int n, int nth)接收2个参数，一个是输入数字，一个是当前数字的位数；

singleDigitToRoman方法中，把罗马数字单个存放在char数组里，方便调用；

char singleRoman[] = {'I','V','X','L','C','D','M','#','#'}; // never use '#'

数组中#都只是用来占位的，避免数组越界；正常情况下都不会出现。

根据输入数字n，分段判断；每段有不同的拼接方式。

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


string singleDigitToRoman(int n, int nth)
{
    if (n ==0)
    {
        return "";
    }

    char singleRoman[] = {'I','V','X','L','C','D','M','#','#'};
    //                     1   5   10  50 100 500 1000
    nth = 2*nth - 1;
    string strResult;

    if (n <= 3)
    {
        strResult.append(n,singleRoman[nth-1]);
    }
    else if (n == 4)
    {
        strResult.push_back(singleRoman[nth-1]);
        strResult.push_back(singleRoman[nth]);
    }
    else if (n == 5)
    {
        strResult.push_back(singleRoman[nth]);
    }
    else if (n >= 6 && n <= 8)
    {
        strResult.push_back(singleRoman[nth]);
        strResult.append(n-5,singleRoman[nth-1]);        
    }
    else if (n == 9)
    {
        strResult.push_back(singleRoman[nth-1]);
        strResult.push_back(singleRoman[nth+1]);
    }
    else
    {
        strResult = "Error";
    }

    return strResult;
}

string intToRoman(int num) 
{
    if (num < 1 || num > 3999)
    {
        return "Invalid Param!";
    }

    string strSingleResult[4];
    int index = 0;
    while (num)
    {
        strSingleResult[index] = singleDigitToRoman(num % 10, index + 1);
        num /= 10;
        ++index;
    }
    
    string strResult;
    while (index > 0)
    {
        strResult += strSingleResult[index-1];
        --index;
    }

    return strResult;
}

TEST(Pratices, tIntToRoman)
{
    //{'I','V','X','L','C','D','M','#','#'};
    //  1   5  10  50  100 500 1000
    // 1
    ASSERT_EQ(intToRoman(1),"I");
    // 99
    ASSERT_EQ(intToRoman(99),"XCIX");
    // 456
    ASSERT_EQ(intToRoman(456),"CDLVI");
    // 3999
    ASSERT_EQ(intToRoman(3999),"MMMCMXCIX");
    // 201
    ASSERT_EQ(intToRoman(201),"CCI");
    // 687
    ASSERT_EQ(intToRoman(687),"DLLXXXVII");
}

参考相关：

http://www.tuicool.com/articles/jIzUZjn