Letter Combinations of a Phone Number
Problem Statement - link #
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.
Examples #
Example 1:
Input: digits = "23"
Output: ["ad","ae","af","bd","be","bf","cd","ce","cf"]
Example 2:
Input: digits = ""
Output: []
Example 3:
Input: digits = "2"
Output: ["a","b","c"]
Constraints #
0 <= digits.length <= 4digits[i]is a digit in the range['2', '9']
Solutions #
class Solution {
public:
map<char,string> mp={
{'2', "abc"}, {'3', "def"}, {'4', "ghi"}, {'5', "jkl"}, {'6', "mno"}, {'7', "pqrs"}, {'8', "tuv"}, {'9', "wxyz"}
};
string temp;
vector<string> res;
void bc(string &d, int i){
if( i==d.size() ){
res.push_back(temp);
return;
}
for(auto c: mp[d[i]]){
temp.push_back(c);
bc(d,i+1);
temp.pop_back();
}
}
vector<string> letterCombinations(string digits) {
if(!digits.size()) return {};
bc(digits,0);
return res;
}
};