学步园

#include <cstdio>
#include <cassert>
#include <iomanip>
#include <list>
#include <iterator>
#include <string>
#include <iostream>
using namespace std;

void Arabic2Roman(int arabic, list<char> & roman)
{
    ......
}

struct Exception
{

};

int Alpha2Bit(char alpha)
{
    switch (alpha)
    {
        case 'I':
        {
            return 0;
        }
        case 'V':
        {
            return 1;
        }
        case 'X':
        {
            return 2;
        }
        case 'L':
        {
            return 3;
        }
        case 'C':
        {
            return 4;
        }
        case 'D':
        {
            return 5;
        }
        case 'M':
        {
            return 6;
        }
        default:
        {
            throw Exception();
            return -1;
        }
    }
}

int Roman2Arabic(const list<char> & roman)
{
    static int const base[] =
    {
        1, 10, 100, 1000
    };

    int arabic = 0;
    int lastbit = 7;
    list<char>::const_reverse_iterator iter = roman.rbegin();
    while (iter != roman.rend())
    {
        int bit = Alpha2Bit(*iter);
        if (bit >= lastbit)
        {
            throw Exception();
            return -1;
        }

        int factor = 0;
        if (0 == bit % 2)
        {
            list<char>::const_reverse_iterator tmpiter = iter;
            ++tmpiter;
            if (tmpiter != roman.rend())
            {
                switch (Alpha2Bit(*tmpiter) - bit)
                {
                    case 0:
                    {
                        factor = 2;
                        iter = tmpiter;
                        ++tmpiter;
                        if (tmpiter != roman.rend() && Alpha2Bit((*tmpiter)) == bit)
                        {
                            ++factor;
                            iter = tmpiter;
                        }
                        break;
                    }
                    case 1:
                    {
                        factor = 4;
                        iter = tmpiter;
                        break;
                    }
                    case 2:
                    {
                        factor = 9;
                        iter = tmpiter;
                        break;
                    }
                    default:
                    {
                        factor = 1;
                        break;
                    }
                }
            }
            else
            {
                factor = 1;
            }
            lastbit = bit;
        }
        else
        {
            factor = 5;
            list<char>::const_reverse_iterator tmpiter = iter;
            ++tmpiter;
            while (tmpiter != roman.rend() && Alpha2Bit(*tmpiter) == bit - 1 && factor < 8)
            {
                ++factor;
                iter = tmpiter;
                ++tmpiter;
            }
            lastbit = bit - 1;
        }
        arabic += factor * base[lastbit / 2];
        ++iter;
    }

    if (0 == arabic)
    {
        throw Exception();
        return -1;
    }
    else
    {
        return arabic;
    }
}

int main()
{
    for (int i = 1; i < 4000; ++i)
    {
        try
        {
            list<char> roman;
            Arabic2Roman(i, roman);
            int arabic = Roman2Arabic(roman);
            if (arabic != i)
            {
                cout << "error conversion : " << endl << '\t';
            }
            cout << setw(4) << i << " -> ";
            for (list<char>::reverse_iterator iter = roman.rbegin(); iter != roman.rend();)
            {
                cout << (*iter);
                ++iter;
            }
            cout << " -> " << arabic << endl;
            if (arabic != i)
            {
                cin.get();
            }
        }
        catch (Exception & e)
        {
            cout << "converse " << i << " throw exception" << endl;
            cin.get();
        }
    }

    cout << "input roman number:";
    string alpha;
    while (cin >> alpha)
    {
        list<char> roman;
        for (string::reverse_iterator iter = alpha.rbegin(); iter != alpha.rend(); ++iter)
        {
            roman.push_back(*iter);
        }

        try
        {
            int arabic = Roman2Arabic(roman);
            cout << '\t' << arabic << endl;
        }
        catch (Exception & e)
        {
            cout << '\t' << "can not converse " << alpha << endl;
        }
    }

    return 0;
}

其中Arabic2Roman()在
试题:将阿拉伯数字转为罗马数字 中有给出实现代码