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package com.yangchd.leetcode.medium;

import java.util.ArrayList;

import java.util.List;

/**

* @author yangchd 2018/6/11.

*

* 17. Letter Combinations of a Phone Number

*

* 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.

*

*/

public class LetterCombinationsOfAPhoneNumber {

class Solution {

public List<String> letterCombinations(String digits) {

List<String> result = new ArrayList<String>();

List<char[]> charList = new ArrayList<char[]>();

for(int i = 0;i<digits.length();i++){

charList.add(getCharByNum(digits.charAt(i)));

}

for (char[] chs : charList) {

if (result.size() > 0 && chs.length > 0) {

List<String> newList = new ArrayList<String>();

for (String str : result) {

for (char ch : chs) {

newList.add(str + String.valueOf(ch));

}

}

result = newList;

} else {

for (char ch : chs) {

result.add(String.valueOf(ch));

}

}

}

return result;

}

private char[] getCharByNum(char num){

switch (num){

case '2':return new char[]{'a','b','c'};

case '3':return new char[]{'d','e','f'};

case '4':return new char[]{'g','h','i'};

case '5':return new char[]{'j','k','l'};

case '6':return new char[]{'m','n','o'};

case '7':return new char[]{'p','q','r','s'};

case '8':return new char[]{'t','u','v'};

case '9':return new char[]{'w','x','y','z'};

default:return null;

}

}

}

}