Magical Word - Practice Problem from Hacker Earth and solution using python 2.7.6

Problem Statement: Dhananjay has recently learned about ASCII values. He is very fond of experimenting. With his knowledge of ASCII values and character he has developed a special word and named it Dhananjay's Magical word.

A word which consist of alphabets whose ASCII values is a prime number is a Dhananjay's Magical word. An alphabet is Dhananjay's Magical alphabet if its ASCII value is prime.

Dhananjay's nature is to boast about the things he know or have learnt about. So just to defame his friends he gives few string to his friends and ask them to convert it to Dhananjay's Magical word. None of his friends would like to get insulted. Help them to convert the given strings to Dhananjay's Magical Word.

Rules for converting:

1.Each character should be replaced by the nearest Dhananjay's Magical alphabet.

2.If the character is equidistant with 2 Magical alphabets. The one with lower ASCII value will be considered as its replacement.

Input format:

First line of input contains an integer T number of test cases. Each test case contains an integer N (denoting the length of the string) and a string S.

Output Format:

For each test case, print Dhananjay's Magical Word in a new line.

Constraints:

1 <= T <= 100

1 <= |S| <= 500

Programming using Python 2.7.6: I solved Dhananjay's Magical Word using python 2.7.6 and below is my code. However before looking in to code you must understand the problem statement:

If you go through the problem statement, it clearly articulated that input format as string - which means user can input any string (e.g. special character, alphanumeric, mix of small and capital alphabet etc). For character (whether it's a numeric, special character or small or capital alphabet) within a given string should be replaced only by nearest alphabet whose ASCII value should be prime (Dhananjay's Magical Number). Again if the character is equidistant to two prime ASCII value of alphabet (Dhananjay's Magical Number) then lower ASCII value should be taken.

Code in Python 2.7: 

Alphabet = ['A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z']

FinalPrimeAlphaASCII = []

#num = int(raw_input())

def isprimenumber(number):

    flag = 0

    for i in range(2,number/2 +1):

        if number % i == 0:

            flag = 1

            break

    if flag == 0:

        return True

for Alpha in Alphabet:

    if isprimenumber(ord(Alpha)): FinalPrimeAlphaASCII.append(ord(Alpha))

magicalword = ''

magicalwords = []  

NumberOfTestCases = int(raw_input())

while (NumberOfTestCases > 0):

    N = int(raw_input())

    userinput = raw_input()

    for s in userinput: # Iterate through each character in given string         

        if ord(s) <= FinalPrimeAlphaASCII[0]: # Any character whose ASCI value less than or equal to 67

            magicalword = magicalword + chr(FinalPrimeAlphaASCII[0])

        elif ord(s) >= FinalPrimeAlphaASCII[len(FinalPrimeAlphaASCII)-1]: # Any character whose ASCI value greater than or equal to 89

            magicalword = magicalword + chr(FinalPrimeAlphaASCII[len(FinalPrimeAlphaASCII)-1])

        elif ord(s) in FinalPrimeAlphaASCII: # Any character whose ASCII value is prime number

            magicalword += s

        else:

            i = 1

            while i < len(FinalPrimeAlphaASCII):

                #print ord(s)

                if ord(s) < FinalPrimeAlphaASCII[i]:

                    #If the character is equi-distant with 2 Magical alphabets.

                    #The one with lower ASCII value will be considered as its replacement

                    if (ord(s) - FinalPrimeAlphaASCII[i-1]) == (FinalPrimeAlphaASCII[i]-ord(s)):

                        magicalword +=chr(FinalPrimeAlphaASCII[i-1])

                        break

                    elif (FinalPrimeAlphaASCII[i]-ord(s)) < (ord(s) - FinalPrimeAlphaASCII[i-1]):

                        magicalword +=chr(FinalPrimeAlphaASCII[i])

                        break

                    else:

                        #Each character should be replaced by the nearest Dhananjay's Magical alphabet.

                        magicalword +=chr(FinalPrimeAlphaASCII[i-1])

                        break

                i +=1

       

           

    magicalwords.append(magicalword)

    magicalword = ''

    NumberOfTestCases -=1

   

for word in magicalwords: print word