PROGRAMMING INTERVIEWS

Question: Convert an roman integer in its decimal equivalent.

Code:

//Assumption: only valid string containing following Roman numerlas are entered.
// MDCLXVI

#include<iostream>
#include<string.h>
using namespace std;

main()
{
char in[10], outn[100];
long int out=0;
cout << "Enter Roman String (Characters allowed are M,D,C,L,X,V,I) : "<<endl;
cin >> in;

int len = strlen(in);
int i = 0;
int lastval = 1000;

while(in[i] != '\0')
{
   switch (in[i])
   {
       case 'M':
       case 'm':
           out = out + 1000;
           if (lastval < 1000)
               out = out - 2*lastval;
           lastval = 1000;
           break;         

       case 'D':
       case 'd':
           out = out + 500;
           if (lastval < 500)
               out = out - 2*lastval;
           lastval = 500;
           break;         

       case 'C':
       case 'c':
           out = out + 100;
           if (lastval < 100)
               out = out - 2*lastval;
           lastval = 100;
           break;         

       case 'L':
       case 'l':
           out = out + 50;
           if (lastval < 50)
               out = out - 2*lastval;
           lastval = 50;
           break;         

       case 'X':
       case 'x':
           out = out + 10;
           if (lastval < 10)
               out = out - 2*lastval;
           lastval = 10;
           break;         

       case 'V':
       case 'v':
           out = out + 5;
           if (lastval < 5)
               out = out - 2*lastval;
           lastval = 5;
           break;         

       case 'I':
       case 'i':
           out = out + 1;
           if (lastval < 1)
               out = out - 2*lastval;
           lastval = 1;
           break;         
  
       default:
           cout << "Invalid Input" <<endl;
           break;
   }
   i++;
}

cout << "Decimal Equivalent = " << out <<endl;
}