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 digits 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" 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'].
class Solution {
public:
void solution(string table[],vector<string> &ans, string digits, int ind,string helper)
{
if(ind>=digits.length())
{
ans.push_back(helper);
return;
}
int num=digits[ind]-'0';
string curr=table[num];
for(int i=0; i<curr.size(); i++)
{
helper.push_back(curr[i]);
solution(table,ans,digits,ind+1,helper);
helper.pop_back();
}
}
vector<string> letterCombinations(string digits) {
string table[10]={" ",".+@$","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};
vector<string> ans;
if(digits.length()==0)return {};
solution(table,ans,digits,0,"");
return ans;
}
};
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