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.
import java.util.*; class Solution { List<String> list=new ArrayList<>(); String[] subs={"abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"}; public List<String> letterCombinations(String digits) { if(digits.isEmpty()) return list; convert("",0,digits); return list; } public void convert(String s,int index,String digits){ if(index==digits.length()){ list.add(s); return; } int sub=digits.charAt(index)-'0'; //System.out.println(sub); String ss=subs[sub-2]; for(int i=0;i<ss.length();i++) convert(s+ss.charAt(i),index+1,digits); } }