### https://theweeklychallenge.org/blog/perl-weekly-challenge-275/
"""

Task 2: Replace Digits

Submitted by: [46]Mohammad Sajid Anwar
     __________________________________________________________________

   You are given an alphanumeric string, $str, where each character is
   either a letter or a digit.

   Write a script to replace each digit in the given string with the value
   of the previous letter plus (digit) places.

Example 1

Input: $str = 'a1c1e1'
Ouput: 'abcdef'

shift('a', 1) => 'b'
shift('c', 1) => 'd'
shift('e', 1) => 'f'

Example 2

Input: $str = 'a1b2c3d4'
Output: 'abbdcfdh'

shift('a', 1) => 'b'
shift('b', 2) => 'd'
shift('c', 3) => 'f'
shift('d', 4) => 'h'

Example 3

Input: $str = 'b2b'
Output: 'bdb'

Example 4

Input: $str = 'a16z'
Output: 'abgz'
     __________________________________________________________________

   Last date to submit the solution 23:59 (UK Time) Sunday 30th June 2024.
     __________________________________________________________________

SO WHAT DO YOU THINK ?
"""
### solution by pokgopun@gmail.com

def replaceDigits1(string: str):
    r = list(string)
    for i in range(len(r)):
        if r[i].isalpha():
            prv = r[i]
        else:
            r[i] = chr(ord(prv)+int(r[i]))
    return "".join(r)

def replaceDigits2(string: str):
    r = ""
    for c in string:
        if c.isalpha():
            prv = c
            r += c
        else:
            r += chr(ord(prv)+int(c))
    return r

import unittest

class TestReplaceDigits(unittest.TestCase):
    def test1(self):
        for inpt,otpt in {
                'a1c1e1': 'abcdef',
                'a1b2c3d4': 'abbdcfdh',
                'b2b': 'bdb',
                'a16z': 'abgz',
                }.items():
            self.assertEqual(replaceDigits1(inpt),otpt)
    def test2(self):
        for inpt,otpt in {
                'a1c1e1': 'abcdef',
                'a1b2c3d4': 'abbdcfdh',
                'b2b': 'bdb',
                'a16z': 'abgz',
                }.items():
            self.assertEqual(replaceDigits2(inpt),otpt)

unittest.main()