[leetcode]Letter Combinations of a Phone Number

实现题 妙的地方在于做一个lookup 的string array

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public class Solution { public List<String> letterCombinations(String digits) { String[] lookup = {" ", " ", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"}; List<String> result = new ArrayList<String>(); List<String> middle = new ArrayList<String>(); for (int i = 0; i < digits.length(); i++){ int number = digits.charAt(i) - '0'; String temp = lookup[number]; for(int j = 0; j < temp.length(); j++){ if (result.isEmpty()){ middle.add(temp.charAt(j)+""); }else{ for(String prev: result){ middle.add(prev+temp.charAt(j)); } } } List<String>tempList = middle; middle = result; result = tempList; middle.clear(); } return result; } }