UVa-11616(Roman Numerals)

Bismillahir Rahmanir Rahim

///Author: Tanvir Ahmmad

///CSE,Islamic University,Bangladesh

#include<iostream>

#include<cstdio>

#include<algorithm>

#include<string>

#include<cstring>

#include<sstream>

#include<cmath>

#include<cstring>

#include<vector>

#include<queue>

#include<map>

#include<set>

#include<stack>

#include<vector>

#include<iterator>

#include <functional> ///sort(arr,arr+n,greater<int>()) for decrement of array

/*every external angle sum=360 degree

  angle find using polygon hand(n) ((n-2)*180)/n*/

///Floor[Log(b)  N] + 1 = the number of digits when any number is represented in base b

using namespace std;

typedef long long ll;

int main()

{

    string str[4009],given;

    string once[]= {"","I","II","III","IV","V","VI","VII","VIII","IX"};

    string twice[]= {"","X","XX","XXX","XL","L","LX","LXX","LXXX","XC"};

    string thrice[]= {"","C","CC","CCC","CD","D","DC","DCC","DCCC","CM"};

    string fourth[]= {"","M","MM","MMM","MMMM","MMMMM","MMMMMM","MMMMMMM","MMMMMMMM","MMMMMMMMM"};

    for(ll i=1; i<=4000; i++)

    {

        ll num=i,arr[98],k=1;

        str[i]="";

        while(num!=0)

            arr[k++]=num%10,num/=10;

        for(ll j=k-1; j>=1; j--)

        {

            if(j==1)

                str[i]+=once[arr[j]];

            else if(j==2)

                str[i]+=twice[arr[j]];

            else if(j==3)

                str[i]+=thrice[arr[j]];

            else if(j==4)

                str[i]+=fourth[arr[j]];

        }

    }

    while(cin>>given)

    {

        if(given[0]>='0' && given[0]<='9') ///Arabic ->-> Roman

        {

            ll given_num=0;

            for(ll i=0; i<given.size(); i++)

                given_num=(given_num*10)+(given[i]-48);

            cout<<str[given_num]<<endl;

        }

        else ///Roman ->-> Arabic

        {

            for(ll i=1; i<=4000; i++)

                if(str[i]==given)

                {

                    cout<<i<<endl;

                    break;

                }

        }

    }

    return 0;

}

///Alhamdulillah

Problem Link:https://onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=24&page=show_problem&problem=2663