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Letter Combinations of a Phone Number

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	`1`	`+'''Leetcode- https://leetcode.com/problems/letter-combinations-of-a-phone-number/ '''`
	`2`	`+'''`
	`3`	`+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.`
	`4`	`+`
	`5`	`+A mapping of digits to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters.`
	`6`	`+`
	`7`	`+Example 1:`
	`8`	`+`
	`9`	`+Input: digits = "23"`
	`10`	`+Output: ["ad","ae","af","bd","be","bf","cd","ce","cf"]`
	`11`	`+`
	`12`	`+'''`
	`13`	`+`
	`14`	`+def letterCombinations(digits):`
	`15`	`+ res = []`
	`16`	`+ digitToChar = { "2": "abc",`
	`17`	`+ "3": "def",`
	`18`	`+ "4": "ghi",`
	`19`	`+ "5": "jkl",`
	`20`	`+ "6": "mno",`
	`21`	`+ "7": "qprs",`
	`22`	`+ "8": "tuv",`
	`23`	`+ "9": "wxyz"}`
	`24`	`+`
	`25`	`+ def backtrack(i,cur):`
	`26`	`+ if len(cur) == len(digits):`
	`27`	`+ res.append(cur)`
	`28`	`+ return`
	`29`	`+`
	`30`	`+ for j in digitToChar[digits[i]]:`
	`31`	`+ backtrack(i+1,cur+j)`
	`32`	`+`
	`33`	`+ if digits:`
	`34`	`+ backtrack(0,"")`
	`35`	`+`
	`36`	`+ return res`
	`37`	`+`
	`38`	`+#T:O(n.4^n)`
	`39`	`+#S:O(n)`
	`40`	`+`
	`41`	`+`

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`@@ -18,5 +18,6 @@ Check the notes for the explaination - [Notes](https://stingy-shallot-4ea.notion`
`18`	`18`	`- [x] [Combination Sum III](Backtracking/216-Combination-Sum-III.py)`
`19`	`19`	`- [x] [Generate Parentheses](Backtracking/22-Generate-Parentheses.py)`
`20`	`20`	`- [x] [Palindrome Partitioning](Backtracking/131-Palindrome-Partitioning.py)`
	`21`	`+ - [x] [Letter Combinations of a Phone Number](Backtracking/17-Letter-Combinations-of-a-Phone-Number.py)`
`21`	`22`
`22`	`23`

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