17. Letter Combinations of a Phone Number
https://leetcode.com/problems/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.
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:
Input: "23" Output: ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].
Note:
Although the above answer is in lexicographical order, your answer could be in any order you want.
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Intuition
Intuition
Traverse the digits string
Take 1 digit at a time
Get the characters for that digit
Get the characters for that digit
For each char, recurse on second digit.. and so on..
We can keep a prefix and add current char there
This will require backtracking once we come back from next digit
StringBuilder has deleteCharAt method or use String, that will create a new object on each recursive call
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We can keep a prefix and add current char there
This will require backtracking once we come back from next digit
StringBuilder has deleteCharAt method or use String, that will create a new object on each recursive call
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