Codewars Python – Integer to Roman conversion

Codewars Python in its 6kyu Kata has given us a problem to convert an integer into the Roman numeral Symbols. In Ancient Roman times, people use Roman numbers instead of integers.

Roman numbers

We can use the Roman symbol for any number.  For e.g instead of 1, we can use I instead of 2 we can use II and instead of 3, we can use III. Remember that we can not use more than 3 identical symbols in a row to show a number. For e.g, we cannot use IIII to represent 4. The Symbols associated with value are: I for 1, V for 5, X for  10,  L for 50,  C for 100, D for 500, and M for 1000. With all these Symbols we can write any number up to 3999.

Codewars Python Solution

The Starter Code that Codewars gave us in Python is

def solution(n):
    # TODO convert int to roman string

    return

To know more about the Problem Discussion click Here

How will you approach this Kata, Comment?

My approach to the Problem:

Firstly, I made two Lists in Python, first to store the Numbers which have Single Roman Symbol Available and Second List for Roman Symbols.

def solution(n):
    # TODO convert int to roman string
    x = [1000,500,100,50,10,5,1] 
    symbol = ["M","D","C","L","X","V","I"]
    val = 0  // indexing the lists
    return_String = "" // return Roman String

Secondly, I started a loop until the Integer given is reduced to 0 the loop goes on.

        while n != 0:
               n   = n % x[val]

My approach to finding the Roman Number was to divide the number by 1000-500-100-50-10-5-1 one by one to get if the number is greater than a specific symbol. For e.g, if we have to find the Roman Symbol for 125 Dividing it by 1000-500 will not do anything but when divide it by 100 we get 125/100 = 1, where I print the 100 Symbol one time which is C after taking modulus we are left with 25, dividing it by 10, we will get 2 so printing  10 Roman Symbol  two times now over String will be like CXX, after taking modulus again left with 5 which has a Symbol V.   So the returned String = CXXV

def solution(n):
    # TODO convert int to roman string
    x = [1000,500,100,50,10,5,1]
    symbol = ["M","D","C","L","X","V","I"]
    val = 0
    return_String = ""
    while n != 0:
        z = int(n/x[val])    
     for i in range(0,z):       
        return_String = return_String + symbol[val]
     n = n % x[val]
     val = val+1
    return return_String

The approach was good but failed on numbers like 4 9, this approach was returning IIII and VIIII respectively. which was wrong. To deal with it I added an if statement that if dividing a number returns 4, it should return the Current symbol concatenated to the previous symbol. For e.g dividing the 4/1 = 4. It should return the current symbol which is I and the Previous symbol which is  V.  Concatenating will return = IV string.

Overall Code

def solution(n):
    # TODO convert int to roman string
    x = [1000,500,100,50,10,5,1]
    symbol = ["M","D","C","L","X","V","I"]
    val = 0
    return_String = ""
    while n != 0:
        z = int(n/x[val])
        if z==4:
            if(symbol[val - 1] == "X" or symbol[val - 1] == "I" or symbol[val - 1] == "C" or symbol[val - 1] == "M" or return_String == "" ):
                return_String = return_String + symbol[val] + symbol[val-1]
            elif(return_String != ""):
                if(return_String[-1] == symbol[val-1]):
                    new = return_String[0:-1] + symbol[val] + symbol[val -2]
                    return_String = new
                else:
                   return_String = return_String + symbol[val] + symbol[val-1] 
                    
        else:
            for i in range(0,z):
                return_String = return_String + symbol[val]
        n = n % x[val]
        val = val+1
    return return_String

When I run it on Codewars it passed all the tests.

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