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Leetcode-Letter Combinations of a Phone Number
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.
Input:Digit string "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.
Solution:
1 public class Solution { 2 public List<String> letterCombinations(String digits) { 3 List<String> res = new ArrayList<String>(); 4 List<List<Character>> map = getMap(); 5 char[] comb = new char[digits.length()]; 6 int[] num = new int[digits.length()]; 7 for (int i=0;i<digits.length();i++) num[i] = (digits.charAt(i)-‘0‘)-2; 8 int[] curPos = new int[digits.length()]; 9 Arrays.fill(curPos,-1);10 int level = 0;11 while (level!=-1){12 if (level>=digits.length()){13 for (int i=0;i<digits.length();i++)14 comb[i] = map.get(num[i]).get(curPos[i]);15 String temp = new String(comb);16 res.add(temp);17 level--;18 continue;19 }20 int val = curPos[level];21 if (val+1>=map.get(num[level]).size()){22 curPos[level]=-1;23 level--;24 continue;25 } else {26 curPos[level]++;27 level++;28 }29 }30 31 return res; 32 }33 34 35 public List<List<Character>> getMap(){36 int[] val = new int[]{3,3,3,3,3,4,3,4};37 List<List<Character>> map = new ArrayList<List<Character>>();38 int base = -1;39 for (int i=0;i<val.length;i++){40 List<Character> list = new ArrayList<Character>();41 for (int j=0;j<val[i];j++){42 base++;43 list.add((char)(‘a‘+base));44 }45 map.add(list);46 }47 return map;48 }49 50 }
Leetcode-Letter Combinations of a Phone Number
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