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Commit 12881a2

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17. Letter Combinations of a Phone Number in C++ (#216)
* Letter Combinations of a Phone Number added * Update README.md * Update README.md
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class Solution {
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public:
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unordered_map<char,string> intToCharsMap;
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void backtracking(string::iterator lf,string::iterator rt,string &path,vector<string> &result)
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{
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if(lf == rt)
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{
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result.push_back(path);
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return;
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}
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for(auto c : intToCharsMap[*lf])
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{
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path.push_back(c);
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backtracking(next(lf,1),rt,path,result);
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path.pop_back(); // if a character doesnot matches then we pop that character from the string and again backtrack.
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}
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}
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vector<string> letterCombinations(string digits)
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{
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int n = digits.size();
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if(digits == "")
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return {};
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string path;
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// result array stores every string that represents that digit.
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vector<string> result;
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intToCharsMap = {
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{'2', "abc"},
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{'3', "def"},
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{'4', "ghi"},
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{'5', "jkl"},
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{'6', "mno"},
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{'7', "pqrs"},
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{'8', "tuv"},
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{'9', "wxyz"},
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};
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backtracking(digits.begin(),digits.end(),path,result);
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return result;
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}
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};

‎README.md

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@@ -364,6 +364,7 @@ Check out ---> [Sample PR](https://github.com/codedecks-in/LeetCode-Solutions/pu
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| 037 | [Sudoku Solver](https://leetcode.com/problems/sudoku-solver/) | [C++](./C++/Sudoku-Solver.cpp) | _O(n^2)_ | _O(1)_ | Hard | Hash Table | |
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| 980 | [Unique Paths III](https://leetcode.com/problems/unique-paths-iii/) | [C++](./C++/Unique-Paths-III.cpp) | _O(R * C * 2 ^ (R \* C))_ | _O(R \* C)_ | Hard | DFS, Memoization | |
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| 39 | [Combination Sum](https://leetcode.com/problems/combination-sum/) | [C++](./C++/combination-sum.cpp) | _O(2^n)_ | _O(n)_ | Medium | Array, Backtracking | |
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| 17 | [Letter Combinations of a Phone Number](https://leetcode.com/problems/letter-combinations-of-a-phone-number/) | [C++](./C++/letter-combinations-of-a-phone-number.cpp) | _O(4^n)_ | _O(n)_ | Medium | String, Hash Table, Backtracking | |
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<br/>
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<div align="right">
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| [Sachin_Upadhyay](https://github.com/sachsbu) <br> <img src="https://avatars.githubusercontent.com/u/24941685?v=4" width="100" height="100"> | India | Java | [GitHub](https://github.com/sachsbu)
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| [Amisha Sahu](https://github.com/Amisha328) <br> <img src = "https://avatars.githubusercontent.com/u/58816552?v=4" width="100" height="100"> | India | C++ | [CodeChef](https://www.codechef.com/users/amisha328)<br/>[LeetCode](https://leetcode.com/Mishi328/)<br/>[HackerRank](https://www.hackerrank.com/amishasahu328)
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| [Shrimadh V Rao](https://github.com/Shrimadh) <br> <img src="https://avatars.githubusercontent.com/u/64469917?v=4" width="100" height="100"> | India | C++ | [GitHub](https://github.com/Shrimadh)
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| [Surbhi Mayank](https://github.com/surbhi2408) <br> <img src="https://avatars.githubusercontent.com/u/58289829?s=400&u=68fd396819b927ec4d8820d87d6d1e311c3abd01&v=4" width="100" height="100"> | India | C++ | [GitHub](https://github.com/surbhi2408)
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<div align="right">
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<b><a href="#algorithms">⬆️ Back to Top</a></b>
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</div>

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