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.

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package leetcode;import java.util.ArrayList;import java.util.List;/** *  * @author Mouse * */public class Solution {public static List<String> letterCombinations2(String digits) {List<String> result = new ArrayList<String>();if (digits.isEmpty()) {result.add("");return result;}String[] map = new String[10];map[0] = null;map[1] = null;map[2] = "abc";map[3] = "def";map[4] = "ghi";map[5] = "jkl";map[6] = "mno";map[7] = "pqrs";map[8] = "tuv";map[9] = "wxyz";int[] number = new int[digits.length()]; // 存储digits中每个字符在循环中的编号，初始为0int k = digits.length() - 1;while (k >= 0) {k = digits.length() - 1;char[] charTemp = new char[digits.length()];for (int i = 0; i < digits.length(); i++) {charTemp[i] = map[digits.charAt(i) - '0'].charAt(number[i]);}result.add(new String(charTemp));while (k >= 0) {if (number[k] < (map[digits.charAt(k) - '0'].length() - 1)) {number[k]++;break;} else {number[k] = 0;k--;}}}return result;}public static void main(String[] args) {String a = "";List<String> b = letterCombinations2(a);System.out.println(b);}}

http://blog.csdn.net/china_wanglong/article/details/38495355