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Abhishek Chaudhary

Posted on

# Letter Combinations of a Phone Number

Given a string containing digits from `2-9` inclusive, return all possible letter combinations that the number could represent. Return the answer in any order.

A mapping of digit to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters.

Example 1:

Input: digits = "23"

Example 2:

Input: digits = ""
Output: []

Example 3:

Input: digits = "2"
Output: ["a","b","c"]

Constraints:

• `0 <= digits.length <= 4`
• `digits[i]` is a digit in the range `['2', '9']`.

SOLUTION:

``````class Solution:
def letterCombinations(self, digits: str) -> List[str]:
comb = {
'2': ['a', 'b', 'c'],
'3': ['d', 'e', 'f'],
'4': ['g', 'h', 'i'],
'5': ['j', 'k', 'l'],
'6': ['m', 'n', 'o'],
'7': ['p', 'q', 'r', 's'],
'8': ['t', 'u', 'v'],
'9': ['w', 'x', 'y', 'z']
}
if len(digits) == 0:
return []
words = [c for c in comb[digits[0]]]
i = 0
while i < len(words):
curr = words[i]
if len(words[i]) == len(digits):
break
if len(curr) < len(digits):
for c in comb[digits[len(curr)]]:
words.append(curr + c)
i += 1
return words[i:]
``````