Find all strings formed from characters mapped to digits of a number in Python

Suppose we have a character mapping as follows, here each digit, from 1 to 9, maps to few characters.

1 -> ['A', 'B', 'C']
2 -> ['D', 'E', 'F']
3 -> ['G', 'H', 'I']
4 -> ['J', 'K', 'L']
5 -> ['M', 'N', 'O']
6 -> ['P', 'Q', 'R']
7 -> ['S', 'T', 'U']
8 -> ['V', 'W', 'X']
9 -> ['Y', 'Z']

If we have a number, we have to change its digits with corresponding characters in given mapping list and show all generated strings. We should consider same character for every occurrence of a digit in the number. The given number will not contain 0.

So, if the input is like [4,3,5], then the output will be

JGM KGM LGM JHM KHM LHM JIM KIM LIM JGN KGN LGN JHN KHN LHN JIN KIN LIN JGO KGO LGO JHO KHO LHO JIO KIO LIO

To solve this, we will follow these steps −

• out := a new list
• temp := a new list
• char_map := a new map
• index := 0
• for each digit in inp, do
  • if digit not in char_map, then
    • char_map[digit] := index
  • clear the temp list
  • for i in range 0 to size of table[digit - 1], do
    • if index is same as 0, then
      • s := table[digit - 1, i]
      • insert s at the end of out
    • if index > 0 is, then
      • for each string in out, do
        • s := table[digit - 1, i]
          • if char_map[digit] is not same as index, then
            • s := string[char_map[digit]]
          • string := string concatenate s
          • insert string at the end of temp
      • if char_map[digit] is not same as index, then
        • break
    • if index > 0 , then
      • out := a copy of temp
    • index := index + 1
  • return out

Example

Let us see the following implementation to get better understanding −

def findCombinations(inp, table):
   out = list()
   temp = list()
   char_map = dict()
   index = 0
   for digit in inp:
      if digit not in char_map:
         char_map[digit] = index
      temp.clear()
      for i in range(len(table[digit - 1])):
         if index == 0:
            s = table[digit - 1][i]
            out.append(s)
         if index > 0:
            for string in out:
               s = table[digit - 1][i]
               if char_map[digit] != index:
                  s = string[char_map[digit]]
               string = string + s
               temp.append(string)
            if char_map[digit] != index:
               break
      if index > 0:
         out = temp.copy()
      index += 1
   return out
mapping = [['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']]
inp = [4,3,5]
res = findCombinations(inp, mapping)
for it in res:
   print(it, end=" ")

Input

[4,3,5]

Output

JGM KGM LGM JHM KHM LHM JIM KIM LIM JGN KGN LGN JHN KHN LHN JIN KIN LIN JGO KGO LGO JHO KHO LHO JIO KIO LIO

Arnab Chakraborty

Published on 23-Jul-2020 12:32:23