package problems.medium;
import java.util.ArrayList;
import java.util.List;
/**
* Created by sherxon on 1/11/17.
*/
public class LetterCombinationsofaPhoneNumber {
List<String> letterCombinations(String digits) {
if (digits == null || digits.length() == 0) return new ArrayList<>();
List<String> list = new ArrayList<>();
getF(digits, 0, "", list);
return list;
}
private void getF(String s, int i, String sf, List<String> list) {
if (i == s.length()) {
list.add(sf);
return;
}
String ss = getMap(i, s);
for (int k = 0; k < ss.length(); k++) {
getF(s, i + 1, sf + ss.charAt(k), list);
}
}
String getMap(int i, String s) {
int c = s.charAt(i) - '0';
String letters = "";
switch (c) {
case 2:
letters = "abc";
break;
case 3:
letters = "def";
break;
case 4:
letters = "ghi";
break;
case 5:
letters = "jkl";
break;
case 6:
letters = "mno";
break;
case 7:
letters = "pqrs";
break;
case 8:
letters = "tuv";
break;
case 9:
letters = "wxyz";
break;
}
return letters;
}
}