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.
思路:使用递归。
public class Solution { List<String> result = new ArrayList<String>(); String[] string = new String[] { " ", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz" }; public List<String> letterCombinations(String digits) { result.add(new String("")); if (digits.length() == 0) return result; letterOfCombinations(digits); return result; } public void letterOfCombinations(String digits) { int tmp = (int) (digits.charAt(0) - '0'); int len = result.size(); int i, j; for (i = 0; i < string[tmp].length() - 1; i++) { for (j = 0; j < len; j++) { result.add(new String(result.get(j))); } } for (i = 0; i < result.size(); i++) { j = i / len; String str = result.get(i) + string[tmp].charAt(j); result.set(i, str); } if (digits.length() == 1) return; letterOfCombinations(digits.substring(1)); } }
LeetCode 18 Letter Combinations of a Phone Number
原文地址:http://blog.csdn.net/mlweixiao/article/details/38984495