# Letter Combinations Of A Phone Number

## Problem

Given a digit string, 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.

## Example

Given 23

Return ["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.

## Code - Java

public class Solution {
/**
* @param digits A digital string
* @return all posible letter combinations
*/
public ArrayList<String> letterCombinations(String digits) {
ArrayList<String> result = new ArrayList<>();
if (digits.length() == 0) {
return result;
}

String[] map = new String[]{" ", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};

char[] c = digits.toCharArray();
for (int i = 0; i < c.length; i++) {
String s = map[c[i] - '0'];
ArrayList<String> tmp = new ArrayList<>();
for (char letter : s.toCharArray()) {
for (String str : result) {
}